x86: Add vendor specific exception vectors

Intel and AMD have some vendor specific exception vectors, namely:
- Intel only: #VE (20),
- AMD only: #HV (28), #VC (29) and #SX (30).

Also Intel's #XM (19) is called #XF for AMD.

Add definitions for all of these and add comments stating they're vendor
specific.

Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20230413184219.36404-4-minipli@grsecurity.net
Signed-off-by: Sean Christopherson <seanjc@google.com>

lib/x86/desc.c

@@ -129,7 +129,11 @@ const char* exception_mnemonic(int vector)
 	VEC(AC);
 	VEC(MC);
 	VEC(XM);
+	VEC(VE);
 	VEC(CP);
+	VEC(HV);
+	VEC(VC);
+	VEC(SX);
 	default: return "#??";
 #undef VEC
 	}

lib/x86/processor.h

@@ -37,7 +37,12 @@
 #define AC_VECTOR 17
 #define MC_VECTOR 18
 #define XM_VECTOR 19
+#define XF_VECTOR XM_VECTOR /* AMD */
+#define VE_VECTOR 20 /* Intel only */
 #define CP_VECTOR 21
+#define HV_VECTOR 28 /* AMD only */
+#define VC_VECTOR 29 /* AMD only */
+#define SX_VECTOR 30 /* AMD only */
 
 #define X86_CR0_PE_BIT		(0)
 #define X86_CR0_PE		BIT(X86_CR0_PE_BIT)