x86/microcode/intel: Get rid of revision_is_newer()

It is a one-liner for checking microcode header revisions. On top of
that, it can be used wrong as it was the case in _save_mc(). Get rid of
it.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>