KVM: SVM: correct the size of spec_ctrl field in VMCB save area

Correct the spec_ctrl field in the VMCB save area based on the AMD
Programmer's manual.

Originally, the spec_ctrl was listed as u32 with 4 bytes of reserved
area.  The AMD Programmer's Manual now lists the spec_ctrl as 8 bytes
in VMCB save area.

The Public Processor Programming reference for Genoa, shows SPEC_CTRL
as 64b register, but the AMD Programmer's Manual lists SPEC_CTRL as
32b register. This discrepancy will be cleaned up in next revision of
the AMD Programmer's Manual.

Since remaining bits above bit 7 are reserved bits in SPEC_CTRL MSR
and thus, not being used, the spec_ctrl added as u32 in the VMCB save
area is currently not an issue.

Fixes: 3dd2775 ("KVM: SVM: Create a separate mapping for the SEV-ES save area")
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Manali Shukla <manali.shukla@amd.com>
Link: https://lore.kernel.org/r/20230717041903.85480-1-manali.shukla@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: Kullu14

arch/x86/include/asm/svm.h

@@ -346,7 +346,7 @@ struct vmcb_save_area {
 	u64 last_excp_from;
 	u64 last_excp_to;
 	u8 reserved_0x298[72];
-	u32 spec_ctrl;		/* Guest version of SPEC_CTRL at 0x2E0 */
+	u64 spec_ctrl;		/* Guest version of SPEC_CTRL at 0x2E0 */
 } __packed;
 
 /* Save area definition for SEV-ES and SEV-SNP guests */
@@ -513,7 +513,7 @@ struct ghcb {
 } __packed;
 
 
-#define EXPECTED_VMCB_SAVE_AREA_SIZE		740
+#define EXPECTED_VMCB_SAVE_AREA_SIZE		744
 #define EXPECTED_GHCB_SAVE_AREA_SIZE		1032
 #define EXPECTED_SEV_ES_SAVE_AREA_SIZE		1648
 #define EXPECTED_VMCB_CONTROL_AREA_SIZE		1024