btrfs: sink gfp parameter to convert_extent_bit

Single caller passes GFP_NOFS. We can get rid of the
gfpflags_allow_blocking checks as NOFS can block but does not recurse to
filesystem through reclaim.

Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 43885e5..98b93d9 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -943,7 +943,7 @@
 
 		err = convert_extent_bit(dirty_pages, start, end,
 					 EXTENT_NEED_WAIT,
-					 mark, &cached_state, GFP_NOFS);
+					 mark, &cached_state);
 		/*
 		 * convert_extent_bit can return -ENOMEM, which is most of the
 		 * time a temporary error. So when it happens, ignore the error