[POWERPC] Cleanup pgtable-ppc32.h

* Removed defines KERNEL_PGD_PTRS & USER_PGD_PTRS since they aren't
  used anywhere
* Changed pmd_page macro to use pfn_to_page so we get proper behavior
  if ARCH_PFN_OFFSET is set as well if we use a different memory model
  on ppc32.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

include/asm-powerpc/pgtable-ppc32.h

@@ -98,9 +98,6 @@ extern int icache_44x_need_flush;
 #define USER_PTRS_PER_PGD	(TASK_SIZE / PGDIR_SIZE)
 #define FIRST_USER_ADDRESS	0
 
-#define USER_PGD_PTRS (PAGE_OFFSET >> PGDIR_SHIFT)
-#define KERNEL_PGD_PTRS (PTRS_PER_PGD-USER_PGD_PTRS)
-
 #define pte_ERROR(e) \
 	printk("%s:%d: bad pte %llx.\n", __FILE__, __LINE__, \
 		(unsigned long long)pte_val(e))
@@ -693,7 +690,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 #define pmd_page_vaddr(pmd)	\
 	((unsigned long) (pmd_val(pmd) & PAGE_MASK))
 #define pmd_page(pmd)		\
-	(mem_map + (__pa(pmd_val(pmd)) >> PAGE_SHIFT))
+	pfn_to_page((__pa(pmd_val(pmd)) >> PAGE_SHIFT))
 #endif
 
 /* to find an entry in a kernel page-table-directory */