x86 microcode: don't check the size

IA32 manual says if micorcode update's size is 0, then the size is
default size (2048 bytes). But this doesn't suggest all microcode
update's size should be above 2048 bytes to me. We actually had a
microcode update whose size is 1024 bytes. The patch just removed the
check.

Backported by Daniel Drake.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>