checkpatch: add warning of future __GFP_NOFAIL use

gfp.h and page_alloc.c already specify that __GFP_NOFAIL is deprecated and
no new users should be added.

Add a warning to checkpatch to catch this.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -4113,6 +4113,12 @@ sub process {
 			     "$1 uses number as first arg, sizeof is generally wrong\n" . $herecurr);
 		}
 
+# check for GFP_NOWAIT use
+		if ($line =~ /\b__GFP_NOFAIL\b/) {
+			WARN("__GFP_NOFAIL",
+			     "Use of __GFP_NOFAIL is deprecated, no new users should be added\n" . $herecurr);
+		}
+
 # check for multiple semicolons
 		if ($line =~ /;\s*;\s*$/) {
 			if (WARN("ONE_SEMICOLON",