Building on FreeBSD 14 seems to be broken

As of today, building on FreeBSD 14 seems to be broken:

```
--- sync_file.o ---
cc -O2 -pipe -fno-strict-aliasing '-DKBUILD_MODNAME="dmabuf"' -DLINUXKPI_VERSION=50000 -DCONFIG_DRM_AMDGPU_CIK -DCONFIG_DRM_AMDGPU_SI -DCONFIG_DRM_AMD_DC -DCONFIG_DRM_AMD_DC_SI -DCONFIG_DRM_I915_FORCE_PROBE='"*"' -DCONFIG_DRM_I915_CAPTURE_ERROR -DCONFIG_DRM_I915_USERFAULT_AUTOSUSPEND=250 -DCONFIG_DRM_I915_STOP_TIMEOUT=100 -DCONFIG_DRM_I915_PREEMPT_TIMEOUT=640 -DCONFIG_DRM_I915_HEARTBEAT_INTERVAL=2500 -DCONFIG_DRM_I915_TIMESLICE_DURATION=1 -DCONFIG_DRM_I915_MAX_REQUEST_BUSYWAIT=8000 -DCONFIG_DRM_I915_FENCE_TIMEOUT=10000 -DCONFIG_DRM_MIPI_DSI -DCONFIG_DRM_PANEL_ORIENTATION_QUIRKS -DCONFIG_DRM_FBDEV_EMULATION -DCONFIG_DRM_FBDEV_OVERALLOC=100 -DCONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG -DCONFIG_BACKLIGHT_CLASS_DEVICE -DCONFIG_DMI -DCONFIG_FB -DCONFIG_MTRR -DCONFIG_PCI -DCONFIG_PM -DCONFIG_SMP -DCONFIG_ACPI -DCONFIG_ACPI_SLEEP -DCONFIG_X86 -DCONFIG_X86_PAT -DCONFIG_64BIT -DCONFIG_AS_MOVNTDQA -DCONFIG_COMPAT -DCONFIG_X86_64 -DCONFIG_DRM_AMD_DC_DCN -DCONFIG_DRM_AMD_DC_DCN3_0 -Werror -D_KERNEL -DKLD_MODULE -nostdinc -I/usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/linuxkpi/gplv2/include -I/usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/linuxkpi/bsd/include -I/usr/src/sys/compat/linuxkpi/common/include -I/usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/linuxkpi/dummy/include -include /usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/obj/usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/dmabuf/opt_global.h -I. -I/usr/src/sys -I/usr/src/sys/contrib/ck/include -fno-common -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -fdebug-prefix-map=./machine=/usr/src/sys/amd64/include -fdebug-prefix-map=./x86=/usr/src/sys/x86/include -fdebug-prefix-map=./i386=/usr/src/sys/i386/include -MD -MF.depend.sync_file.o -MTsync_file.o -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float -fno-asynchronous-unwind-tables -ffreestanding -fwrapv -fstack-protector -Wall -Wnested-externs -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wcast-qual -Wundef -Wno-pointer-sign -D__printf__=__freebsd_kprintf__ -Wmissing-include-dirs -fdiagnostics-show-option -Wno-unknown-pragmas -Wno-error=tautological-compare -Wno-error=empty-body -Wno-error=parentheses-equality -Wno-error=unused-function -Wno-error=pointer-sign -Wno-error=shift-negative-value -Wno-address-of-packed-member -Wno-format-zero-length -mno-aes -mno-avx -std=iso9899:1999 -c /usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/drivers/dma-buf/sync_file.c -o sync_file.o
/usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/drivers/dma-buf/sync_file.c:394:3: error: implicit declaration of function 'cpu_relax' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
cpu_relax();
^
/usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/drivers/dma-buf/sync_file.c:394:3: note: did you mean 'cpu_reset'?
./machine/cpu.h:81:6: note: 'cpu_reset' declared here
void cpu_reset(void);
^
1 error generated.
*** [sync_file.o] Error code 1
make[2]: stopped in /usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/dmabuf
1 error
make[2]: stopped in /usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8/dmabuf
make[1]: stopped in /usr/ports/graphics/drm-510-kmod/work/drm-kmod-drm_v5.10.113_8
===> Compilation failed unexpectedly.
Try to set MAKE_JOBS_UNSAFE=yes and rebuild before reporting the failure to
the maintainer.
*** Error code 1
Stop.
make: stopped in /usr/ports/graphics/drm-510-kmod
```

https://cirrus-ci.com/task/6715639216734208

It had been working before.
What gives?