ARM: pgtable: add pud-level code

Add pud_offset() et.al. between the pgd and pmd code in preparation of
using pgtable-nopud.h rather than 4level-fixup.h.

This incorporates a fix from Jamie Iles <jamie@jamieiles.com> for
uaccess_with_memcpy.c.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index ca56791..5750704 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -301,6 +301,7 @@
 #define pgd_present(pgd)	(1)
 #define pgd_clear(pgdp)		do { } while (0)
 #define set_pgd(pgd,pgdp)	do { } while (0)
+#define set_pud(pud,pudp)	do { } while (0)
 
 
 /* Find an entry in the second-level page table.. */