KVM: x86/mmu: Pretty print PK, SS, and SGX flags in MMU tracepoints

Add PK (Protection Keys), SS (Shadow Stacks), and SGX (Software Guard
Extensions) to the set of #PF error flags handled via
kvm_mmu_trace_pferr_flags.  While KVM doesn't expect PK or SS #PFs in
particular, pretty print their names instead of the raw hex value saves
the user from having to go spelunking in the SDM to figure out what's
going on.

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20250919223258.1604852-23-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/mmu/mmutrace.h

@@ -51,6 +51,9 @@
 	{ PFERR_PRESENT_MASK, "P" },	\
 	{ PFERR_WRITE_MASK, "W" },	\
 	{ PFERR_USER_MASK, "U" },	\
+	{ PFERR_PK_MASK, "PK" },	\
+	{ PFERR_SS_MASK, "SS" },	\
+	{ PFERR_SGX_MASK, "SGX" },	\
 	{ PFERR_RSVD_MASK, "RSVD" },	\
 	{ PFERR_FETCH_MASK, "F" }