x86: unify KERNEL_PGD_PTRS

Make KERNEL_PGD_PTRS common, as previously it was only being defined
for 32-bit.

There are a couple of follow-on changes from this:
 - KERNEL_PGD_PTRS was being defined in terms of USER_PGD_PTRS.  The
   definition of USER_PGD_PTRS doesn't really make much sense on x86-64,
   since it can have two different user address-space configurations.
   I renamed USER_PGD_PTRS to KERNEL_PGD_BOUNDARY, which is meaningful
   for all of 32/32, 32/64 and 64/64 process configurations.

 - USER_PTRS_PER_PGD was also defined and was being used for similar
   purposes.  Converting its users to KERNEL_PGD_BOUNDARY left it
   completely unused, and so I removed it.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Zach Amsden <zach@vmware.com>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h
index 4ebea41..e61075e 100644
--- a/include/asm-x86/pgtable.h
+++ b/include/asm-x86/pgtable.h
@@ -1,7 +1,6 @@
 #ifndef _ASM_X86_PGTABLE_H
 #define _ASM_X86_PGTABLE_H
 
-#define USER_PTRS_PER_PGD	((TASK_SIZE-1)/PGDIR_SIZE+1)
 #define FIRST_USER_ADDRESS	0
 
 #define _PAGE_BIT_PRESENT	0	/* is present */
@@ -330,6 +329,9 @@
 # include "pgtable_64.h"
 #endif
 
+#define KERNEL_PGD_BOUNDARY	pgd_index(PAGE_OFFSET)
+#define KERNEL_PGD_PTRS		(PTRS_PER_PGD - KERNEL_PGD_BOUNDARY)
+
 #ifndef __ASSEMBLY__
 
 enum {