include/linux/gfp.h: exclude duplicate header

mmdebug.h is included twice.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/gfp.h

@@ -6,7 +6,6 @@
 #include <linux/stddef.h>
 #include <linux/linkage.h>
 #include <linux/topology.h>
-#include <linux/mmdebug.h>
 
 struct vm_area_struct;