Since kernel modules can now contain sections of type SHT_AMD64_UNWIND,
the boot loader should not skip over these anymore while loading images.
Otherwise the kernel can still panic when it doesn't find the .eh_frame
section belonging to the .rela.eh_frame section.

Unfortunately this will require installing boot loaders from sys/boot
before attempting to boot with a new kernel.

Reviewed by: kib
MFC after: 2 weeks
X-MFC-With: r296419