mm: use alloc_pages_exact() in alloc_large_system_hash() to avoid duplicated logic

		else if (hashdist)

			table = __vmalloc(size, GFP_ATOMIC, PAGE_KERNEL);

		else {

			unsigned long order = get_order(size);

			if (order < MAX_ORDER)

				table = (void *)__get_free_pages(GFP_ATOMIC,

								order);

			/*

			 * If bucketsize is not a power-of-two, we may free

			 * some pages at the end of hash table.

			 */

			if (table) {

				unsigned long alloc_end = (unsigned long)table +

						(PAGE_SIZE << order);

				unsigned long used = (unsigned long)table +

						PAGE_ALIGN(size);

				split_page(virt_to_page(table), order);

				while (used < alloc_end) {

					free_page(used);

					used += PAGE_SIZE;

				}

			}

			 * some pages at the end of hash table which

			 * alloc_pages_exact() automatically does

			 */

			if (get_order(size) < MAX_ORDER)

				table = alloc_pages_exact(size, GFP_ATOMIC);

		}

	} while (!table && size > PAGE_SIZE && --log2qty);