KVM: MMU: Rename PT64_ROOT_LEVEL to PT64_ROOT_4LEVEL.

Now we have 4 level page table and 5 level page table in 64 bits
long mode, let's rename the PT64_ROOT_LEVEL to PT64_ROOT_4LEVEL,
then we can use PT64_ROOT_5LEVEL for 5 level page table, it's
helpful to make the code more clear.

Also PT64_ROOT_MAX_LEVEL is defined as 4, so that we can just
redefine it to 5 whenever a replacement is needed for 5 level
paging.

Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -315,8 +315,10 @@ struct kvm_pio_request {
 	int size;
 };
 
+#define PT64_ROOT_MAX_LEVEL 4
+
 struct rsvd_bits_validate {
-	u64 rsvd_bits_mask[2][4];
+	u64 rsvd_bits_mask[2][PT64_ROOT_MAX_LEVEL];
 	u64 bad_mt_xwr;
 };