scripts/checkpatch.pl: __GFP_NOFAIL isn't going away

Revert commit 7e4915e7 ("checkpatch: add warning of future
__GFP_NOFAIL use").

There are no plans to remove __GFP_NOFAIL.

__GFP_NOFAIL exists to

a) centralise the retry-allocation-for-ever operation into the core
   allocator, which is the appropriate implementation site and

b) permit us to identify code sites which aren't handling memory
   exhaustion appropriately.

Cc: David Rientjes <rientjes@google.com>
Cc: Joe Perches <joe@perches.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>