x86/cpufeatures: Add X86_FEATURE_RDS

x86/cpufeatures: Add X86_FEATURE_RDS

Add the CPU feature bit CPUID.7.0.EDX[31] which indicates whether the CPU
supports Reduced Data Speculation.

[ tglx: Split it out from a later patch ]

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: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit 0cc5fa00b0a88dad140b4e5c2cead9951ad36822)
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 called cpufeature.h]
[We also need to use the scattered function to set the flag similar
 to how the rest of CPUID.7.0.EDX[31] are done]

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