KVM: MMU: Replace role.glevels with role.cr4_pae

There is no real distinction between glevels=3 and glevels=4; both have
exactly the same format and the code is treated exactly the same way.  Drop
role.glevels and replace is with role.cr4_pae (which is meaningful).  This
simplifies the code a bit.

As a side effect, it allows sharing shadow page tables between pae and
longmode guest page tables at the same guest page.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3602728..707d272 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -171,8 +171,8 @@
 union kvm_mmu_page_role {
 	unsigned word;
 	struct {
-		unsigned glevels:4;
 		unsigned level:4;
+		unsigned cr4_pae:1;
 		unsigned quadrant:2;
 		unsigned pad_for_nice_hex_output:6;
 		unsigned direct:1;