x86/cpufeature: Provide helper to set bugs bits

Will be used in a later patch to set bug bits for bugs which need late
detection.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20161209182912.2726-2-bp@alien8.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>