Introduce ___GFP_* masks in order for gfp_t to not be mixed with plain
integers which causes a lot of warnings like the following:

 warning: restricted gfp_t degrades to integer
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>