KVM: x86/mmu: pass PFERR_GUEST_PAGE/FINAL_MASK to kvm_translate_gpa

KVM: x86/mmu: pass PFERR_GUEST_PAGE/FINAL_MASK to kvm_translate_gpa

The XS/XU bit for EPT are only applied to final accesses, and use the
U bit from the page walk itself.  While strictly speaking not necessary
(any value of PFERR_USER_MASK would be the same for page table accesses,
because they're reads and writes only), it is clearer and less hackish
to only apply MBEC to PFERR_GUEST_FINAL_MASK.  Allow kvm-intel.ko to
distinguish the two cases.

Tested-by: David Riley <d.riley@proxmox.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>