firmware/guest: add ALIAS_CHECK_COMPLETE to attestation report

After mitigating CVE-2024-21944, SEV firmware exposes a new bit to the
guest attestation report confirming the mitigation of the CVE.  Include
this bit in the report.

The bit is currently documented in the security bulletin page (below),
and will be included in the spec in its next update.

https://www.amd.com/en/resources/product-security/bulletin/amd-sb-3015.html

Signed-off-by: Amit Shah <amit.shah@amd.com>

src/firmware/guest/types/snp.rs

@@ -473,7 +473,8 @@ bitfield! {
     /// Bit 2 indicates if ECC memory is used.
     /// Bit 3 indicates if RAPL is disabled.
     /// Bit 4 indicates if ciphertext hiding is enabled
-    /// Bits 5-63 are reserved.
+    /// Bit 5 indicates if DRAM alias check is complete (CVE-2024-21944)
+    /// Bits 6-63 are reserved.
     #[repr(C)]
     #[derive(Default, Deserialize, Clone, Copy, Serialize)]
     pub struct PlatformInfo(u64);
@@ -488,8 +489,10 @@ bitfield! {
     pub rapl_disabled, _: 3, 3;
     /// Indicates that ciphertext hiding is enabled
     pub ciphertext_hiding_enabled, _: 4, 4;
+    /// Indicates that DRAM alias check is complete
+    pub dram_alias_check_complete, _: 5, 5;
     /// reserved
-    reserved, _: 5, 63;
+    reserved, _: 6, 63;
 }
 
 impl Display for PlatformInfo {
@@ -503,13 +506,15 @@ Platform Info ({}):
   ECC Enabled:               {}
   RAPL Disabled:             {}
   Ciphertext Hiding Enabled: {}
+  DRAM Alias Check Complete: {}
 "#,
             self.0,
             self.smt_enabled(),
             self.tsme_enabled(),
             self.ecc_enabled(),
             self.rapl_disabled(),
             self.ciphertext_hiding_enabled(),
+            self.dram_alias_check_complete(),
         )
     }
 }