remove dead code in pgtable_cache_init

The conversion from using a slab cache to quicklist left some residual
dead code.

I note that in the conversion it now always allocates a whole page for
the pgd, rather than the 32 bytes needed for a PAE pgd.  Was this
intended?
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Cc: William Lee Irwin III <wli@holomorphy.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>

arch/x86/mm/init_32.c

@@ -746,24 +746,12 @@ struct kmem_cache *pmd_cache;
 
 void __init pgtable_cache_init(void)
 {
-	size_t pgd_size = PTRS_PER_PGD*sizeof(pgd_t);
-
-	if (PTRS_PER_PMD > 1) {
+	if (PTRS_PER_PMD > 1)
 		pmd_cache = kmem_cache_create("pmd",
 					      PTRS_PER_PMD*sizeof(pmd_t),
 					      PTRS_PER_PMD*sizeof(pmd_t),
 					      SLAB_PANIC,
 					      pmd_ctor);
-		if (!SHARED_KERNEL_PMD) {
-			/* If we're in PAE mode and have a non-shared
-			   kernel pmd, then the pgd size must be a
-			   page size.  This is because the pgd_list
-			   links through the page structure, so there
-			   can only be one pgd per page for this to
-			   work. */
-			pgd_size = PAGE_SIZE;
-		}
-	}
 }
 
 /*