x86/cpufeatures: Re-enable ENQCMD

The ENQCMD feature can only be used if CONFIG_INTEL_IOMMU_SVM is set.
Add X86_FEATURE_ENQCMD to the disabled features mask as appropriate so
that cpu_feature_enabled() can be used to check the feature.

  [ bp: Massage commit message. ]

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220207230254.3342514-10-fenghua.yu@intel.com