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/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 6a92539..2de2f7a 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1039,8 +1039,8 @@
 
 #ifdef CONFIG_X86_32
 	/* init low mem mapping */
-	clone_pgd_range(swapper_pg_dir, swapper_pg_dir + USER_PGD_PTRS,
-			min_t(unsigned long, KERNEL_PGD_PTRS, USER_PGD_PTRS));
+	clone_pgd_range(swapper_pg_dir, swapper_pg_dir + KERNEL_PGD_BOUNDARY,
+			min_t(unsigned long, KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
 	flush_tlb_all();
 #endif