CVE-2018-3639 (x86)

cpu_show_common() is not used outside of arch/x86/kernel/cpu/bugs.c, so
make it static.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
[juergh: Context adjustments.]
Signed-off-by: Juerg Haefliger <juergh@canonical.com>