x86: clean up pte_exec

- Rename it to pte_exec() from pte_exec_kernel(). There is nothing
kernel specific in there.
- Move it into the common file because _PAGE_NX is 0 on !PAE and then
pte_exec() will be always evaluate to true.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 724a5ef..5080646 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -542,7 +542,7 @@
 	pte = lookup_address(vaddr);
 	BUG_ON(!pte);
 
-	if (!pte_exec_kernel(*pte))
+	if (!pte_exec(*pte))
 		ret = 0;
 
 	if (enable)