mm: use macros from compiler.h instead of __attribute__((...))

To increase compiler portability there is <linux/compiler.h> which
provides convenience macros for various gcc constructs.  Eg: __weak for
__attribute__((weak)).  I've replaced all instances of gcc attributes with
the right macro in the memory management (/mm) subsystem.

[akpm@linux-foundation.org: while-we're-there consistency tweaks]
Signed-off-by: Gideon Israel Dsouza <gidisrael@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/nommu.c

@@ -25,6 +25,7 @@
 #include <linux/vmalloc.h>
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
+#include <linux/compiler.h>
 #include <linux/mount.h>
 #include <linux/personality.h>
 #include <linux/security.h>
@@ -460,7 +461,7 @@ EXPORT_SYMBOL_GPL(vm_unmap_aliases);
  * Implement a stub for vmalloc_sync_all() if the architecture chose not to
  * have one.
  */
-void  __attribute__((weak)) vmalloc_sync_all(void)
+void __weak vmalloc_sync_all(void)
 {
 }