btrfs: drop unused argument from extent_io_tree_init

all callers pass GFP_NOFS, but the GFP mask argument is not used in the
function; GFP_ATOMIC is passed to radix tree initialization and it's the
only correct one, since we're using the preload/insert mechanism of
radix tree.
Let's drop the gfp mask from btrfs function, this will not change
behaviour.

Signed-off-by: David Sterba <dsterba@suse.cz>

fs/btrfs/extent_io.c

@@ -101,7 +101,7 @@ void extent_io_exit(void)
 }
 
 void extent_io_tree_init(struct extent_io_tree *tree,
-			  struct address_space *mapping, gfp_t mask)
+			 struct address_space *mapping)
 {
 	tree->state = RB_ROOT;
 	INIT_RADIX_TREE(&tree->buffer, GFP_ATOMIC);