Hibernate: Replace unnecessary evaluation of pfn_to_page()

Replace one evaluation of pfn_to_page() in copy_data_pages() with
the value of a local variable containing the right number already.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Len Brown <len.brown@intel.com>

kernel/power/snapshot.c

@@ -981,7 +981,7 @@ static void copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
 			 * data modified by kmap_atomic()
 			 */
 			safe_copy_page(buffer, s_page);
-			dst = kmap_atomic(pfn_to_page(dst_pfn), KM_USER0);
+			dst = kmap_atomic(d_page, KM_USER0);
 			memcpy(dst, buffer, PAGE_SIZE);
 			kunmap_atomic(dst, KM_USER0);
 		} else {