x86/microcode/amd: Remove unneeded break

A break is not needed if it is preceded by a return.

Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201019200629.17247-1-trix@redhat.com