KVM: SVM: Rename vmplX_ssp -> plX_ssp

The SSP fields in the SEV-ES save area were mistakenly named vmplX_ssp
instead of plX_ssp. Rename these to the correct names as defined in the
APM.

Fixes: 6d3b3d3 ("KVM: SVM: Update the SEV-ES save area mapping")
Signed-off-by: John Allen <john.allen@amd.com>
Link: https://lore.kernel.org/r/20240227200356.35114-1-john.allen@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/include/asm/svm.h

@@ -358,10 +358,10 @@ struct sev_es_save_area {
 	struct vmcb_seg ldtr;
 	struct vmcb_seg idtr;
 	struct vmcb_seg tr;
-	u64 vmpl0_ssp;
-	u64 vmpl1_ssp;
-	u64 vmpl2_ssp;
-	u64 vmpl3_ssp;
+	u64 pl0_ssp;
+	u64 pl1_ssp;
+	u64 pl2_ssp;
+	u64 pl3_ssp;
 	u64 u_cet;
 	u8 reserved_0xc8[2];
 	u8 vmpl;