Installation failed: the boot and root partitions are on separate disks

When running bootc install on disk that boot and root partitions are on separate disks, like following:
```
[root@nvidia-jetson-agx-orin-03 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
mmcblk0 179:0 0 59.3G 0 disk
├─mmcblk0p1 179:1 0 600M 0 part /boot/efi
└─mmcblk0p2 179:2 0 1G 0 part /boot
mmcblk0boot0 179:8 0 31.5M 1 disk
mmcblk0boot1 179:16 0 31.5M 1 disk
nvme0n1 259:0 0 465.8G 0 disk
└─nvme0n1p1 259:1 0 465.8G 0 part /
```

Run bootc install using `quay.io/centos-bootc/centos-bootc:stream9` failed with command:
```
podman run \
--rm --privileged \
-v /dev:/dev \
-v /var/lib/containers:/var/lib/containers \
-v /:/target \
--pid=host --security-opt label=type:unconfined_t \
quay.io/centos-bootc/centos-bootc:stream9 \
env BOOTC_BOOTLOADER_DEBUG=1 RUST_LOG=trace bootc install to-existing-root --skip-fetch-check --acknowledge-destructive --root-ssh-authorized-keys /target/root/.ssh/id_rsa.pub --karg=console=ttyS0,115200n8
```
From the logs, we passed device `/dev/nvme0n1`, but it should be `/dev/mmcblk0`
```
Bootloader: grub
Installing bootloader via bootupd
[TRACE bootupd] executing cli
[DEBUG bootupd::efi] Found metadata grub2-efi-aa64-1:2.06-120.el9.aarch64,shim-aa64-15.8-2.el9.aarch64
[DEBUG bootupd::efi] Reusing existing mount point "/target/boot/efi"
[DEBUG bootupd::efi] Get product name: 'CentOS Stream'
[DEBUG bootupd::efi] Unmounting
[TRACE bootupd::efi] Unmounted
error: boot data installation failed: installing component EFI: Updating EFI firmware variables: Failed to find ESP device
error: Installing to filesystem: Installing bootloader: Failed to run command: Command {
program: "bootupctl",
args: [
"bootupctl",
"backend",
"install",
"--write-uuid",
"-vvvv",
"--update-firmware",
"--auto",
"--src-root",
"/target/ostree/deploy/default/deploy/74cb3048605f17a48123e00e498ab2cea020f872dc7b02f6be6425e1b36d29ef.0",
"--device",
"/dev/nvme0n1",
"/target",
],
create_pidfd: false,
}
```