x86/feature: Enable the x86 feature to control

x86/feature: Enable the x86 feature to control

cpuid ax=0x7, return rdx bit 26 to indicate presence of this feature
IA32_SPEC_CTRL (0x48) and IA32_PRED_CMD (0x49)
IA32_SPEC_CTRL, bit0 – Indirect Branch Restricted Speculation (IBRS)
IA32_PRED_CMD,  bit0 – Indirect Branch Prediction Barrier (IBPB)

Orabug: 27344012
CVE: CVE-2017-5715

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>