The new U-Boot supports the phone's MMC controllers, so let's use that to enable UEFI boot. This allows us to drop initfs-extra, avoid reflashing the kernel to the boot partition every upgrade, fix kernel-cmdline and future-proof the port in general. Signed-off-by: Duje Mihanović <duje@dujemihanovic.xyz> Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/8337>