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 <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Tony Luck <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Fenghua Yu

arch/x86/include/asm/disabled-features.h

@@ -56,8 +56,11 @@
 # define DISABLE_PTI		(1 << (X86_FEATURE_PTI & 31))
 #endif
 
-/* Force disable because it's broken beyond repair */
-#define DISABLE_ENQCMD		(1 << (X86_FEATURE_ENQCMD & 31))
+#ifdef CONFIG_INTEL_IOMMU_SVM
+# define DISABLE_ENQCMD		0
+#else
+# define DISABLE_ENQCMD		(1 << (X86_FEATURE_ENQCMD & 31))
+#endif
 
 #ifdef CONFIG_X86_SGX
 # define DISABLE_SGX	0