x86/microcode/AMD: Have __apply_microcode_amd() return bool

commit 78e0aadb upstream

This is the natural thing to do anyway.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>