EFI_PXE_BASE_CODE_DHCPV6_PACKET is in gnu-efi-3.0t
Make sure all the Makefiles use the same arguments for mmx/sse/ms_abi.

Signed-off-by: Peter Jones <pjones@redhat.com>
Remove FALLBACK_OBJS during clean as well.

Signed-off-by: Peter Jones <pjones@redhat.com>