i7-8665U: Linux often freezes at beginning of start when on battery

(No idea, if related to https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/35, so I split it out.)

On a Dell Precision 3540/0M14W7, BIOS 1.9.1 07/06/2020, being on battery (power cable not plugged in) Linux often freezes when loaded from GRUB. GRUB’s loading initrd status message is the last thing visible. The LUKS passphrase dialog does not appear.

In our case, plugging in the power cable or starting with `maxcpus=1` fixes the issue. But starting with maxcpus=1, and bringing CPUs online in GNU/Linux still sometimes causes freezes after one or two CPUs.

```
$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
Address sizes: 39 bits physical, 48 bits virtual
CPU(s): 8
On-line CPU(s) list: 0-7
Thread(s) per core: 2
Core(s) per socket: 4
Socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 142
Model name: Intel(R) Core(TM) i7-8665U CPU @ 1.90GHz
Stepping: 12
CPU MHz: 998.859
CPU max MHz: 4800.0000
CPU min MHz: 400.0000
BogoMIPS: 4199.88
Virtualization: VT-x
L1d cache: 128 KiB
L1i cache: 128 KiB
L2 cache: 1 MiB
L3 cache: 8 MiB
NUMA node0 CPU(s): 0-7
Vulnerability Itlb multihit: KVM: Mitigation: VMX disabled
Vulnerability L1tf: Not affected
Vulnerability Mds: Not affected
Vulnerability Meltdown: Not affected
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp
Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2: Mitigation; Enhanced IBRS, IBPB conditional, RSB filling
Vulnerability Srbds: Mitigation; TSX disabled
Vulnerability Tsx async abort: Mitigation; TSX disabled
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm p
be syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aper
fmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic mo
vbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single ssbd
ibrs ibpb stibp ibrs_enhanced tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 e
rms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_no
tify hwp_act_window hwp_epp md_clear flush_l1d arch_capabilities
```

Unforutnately, no new microcode updates are shipped in the latest Intel release, *intel-microcode* 3.20201110.1, so it’d be great if after several months this was looked at.