Generic page_is_ram: use __weak

Use __weak instead of __attribute__((weak)).

Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/kernel/resource.c b/kernel/resource.c
index b4d637a..e68cd74 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -305,7 +305,7 @@
  * This generic page_is_ram() returns true if specified address is
  * registered as "System RAM" in iomem_resource list.
  */
-int __attribute__((weak)) page_is_ram(unsigned long pfn)
+int __weak page_is_ram(unsigned long pfn)
 {
 	return walk_system_ram_range(pfn, 1, NULL, __is_ram) == 1;
 }