KVM: x86: assign two bits to track SPTE kinds

Currently, we are overloading SPTE_SPECIAL_MASK to mean both
"A/D bits unavailable" and MMIO, where the difference between the
two is determined by mio_mask and mmio_value.

However, the next patch will need two bits to distinguish
availability of A/D bits from write protection.  So, while at
it give MMIO its own bit pattern, and move the two bits from
bit 62 to bits 52..53 since Intel is allocating EPT page table
bits from the top.

Reviewed-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -219,13 +219,6 @@ enum {
 				 PFERR_WRITE_MASK |		\
 				 PFERR_PRESENT_MASK)
 
-/*
- * The mask used to denote special SPTEs, which can be either MMIO SPTEs or
- * Access Tracking SPTEs. We use bit 62 instead of bit 63 to avoid conflicting
- * with the SVE bit in EPT PTEs.
- */
-#define SPTE_SPECIAL_MASK (1ULL << 62)
-
 /* apic attention bits */
 #define KVM_APIC_CHECK_VAPIC	0
 /*