x86/bugs: Expose /sys/../spec_store_bypass

x86/bugs: Expose /sys/../spec_store_bypass

Add the sysfs file for the new vulerability. It does not do much except
show the words 'Vulnerable' for recent x86 cores.

Intel cores prior to family 6 are known not to be vulnerable, and so are
some Atoms and some Xeon Phi.

It assumes that older Cyrix, Centaur, etc. cores are immune.

OraBug: 28041771
CVE: CVE-2018-3639

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit c456442cd3a59eeb1d60293c26cbe2ff2c4e42cf)
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Mihai Carabas <mihai.carabas@oracle.com>
 Conflicts:
	arch/x86/include/asm/cpufeatures.h
[It is a different file - cpufeature.h]

	arch/x86/kernel/cpu/bugs.c
[As well, called bugs_64.c]

	arch/x86/kernel/cpu/common.c
[Location of cpu_set_bug_bits is different and also had to drop the __initconst]

Signed-off-by: Brian Maly <brian.maly@oracle.com>