x86/sev: Indicate the SEV-SNP guest supports Secure AVIC

Now that Secure AVIC support is complete, make it part of to the SNP present
features.

Co-developed-by: Kishon Vijay Abraham I <[e-mail]>
Signed-off-by: Kishon Vijay Abraham I <[e-mail]>
Signed-off-by: Neeraj Upadhyay <[e-mail]>
Signed-off-by: Borislav Petkov (AMD) <[e-mail]>
Reviewed-by: Tianyu Lan <[e-mail]>
Link: https://lore.kernel.org/[e-mail]

arch/x86/boot/compressed/sev.c

···
 				 MSR_AMD64_SNP_SECURE_AVIC |		\
 				 MSR_AMD64_SNP_RESERVED_MASK)
 
+#ifdef CONFIG_AMD_SECURE_AVIC
+#define SNP_FEATURE_SECURE_AVIC		MSR_AMD64_SNP_SECURE_AVIC
+#else
+#define SNP_FEATURE_SECURE_AVIC		0
+#endif
+
 /*
  * SNP_FEATURES_PRESENT is the mask of SNP features that are implemented
  * by the guest kernel. As and when a new feature is implemented in the
  * guest kernel, a corresponding bit should be added to the mask.
  */
 #define SNP_FEATURES_PRESENT	(MSR_AMD64_SNP_DEBUG_SWAP |	\
-				 MSR_AMD64_SNP_SECURE_TSC)
+				 MSR_AMD64_SNP_SECURE_TSC |	\
+				 SNP_FEATURE_SECURE_AVIC)
 
 u64 snp_get_unsupported_features(u64 status)
 {