Remove the restriction that the kernel needs to be loaded at the bottom of

Remove the restriction that the kernel needs to be loaded at the bottom of
physical memory.  This makes it possible to boot OpenBSD on platforms that
have physical memory start at address 0x00000000 as the EFI bootloader will
only attempt to load kernels at address 0x10000000 and above to work around
a bug in the u-boot EFI API layer.

ok patrick@