openrisc: fix PTRS_PER_PGD define

On OpenRISC, with its 8k pages, PAGE_SHIFT is defined to be 13.
That makes the expression (1UL << (PAGE_SHIFT-2)) evaluate
to 2048.
The correct value for PTRS_PER_PGD should be 256.

Correcting the PTRS_PER_PGD define unveiled a bug in map_ram(),
where PTRS_PER_PGD was used when the intent was to iterate
over a set of page table entries.
This patch corrects that issue as well.
Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Acked-by: Jonas Bonn <jonas@southpole.se>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Stafford Horne <shorne@gmail.com>

arch/openrisc/include/asm/pgtable.h

@@ -69,7 +69,7 @@ extern void paging_init(void);
  */
 #define PTRS_PER_PTE	(1UL << (PAGE_SHIFT-2))
 
-#define PTRS_PER_PGD	(1UL << (PAGE_SHIFT-2))
+#define PTRS_PER_PGD	(1UL << (32-PGDIR_SHIFT))
 
 /* calculate how many PGD entries a user-level program can use
  * the first mappable virtual address is 0

arch/openrisc/mm/init.c

@@ -110,7 +110,7 @@ static void __init map_ram(void)
 			set_pmd(pme, __pmd(_KERNPG_TABLE + __pa(pte)));
 
 			/* Fill the newly allocated page with PTE'S */
-			for (j = 0; p < e && j < PTRS_PER_PGD;
+			for (j = 0; p < e && j < PTRS_PER_PTE;
 			     v += PAGE_SIZE, p += PAGE_SIZE, j++, pte++) {
 				if (v >= (u32) _e_kernel_ro ||
 				    v < (u32) _s_kernel_ro)