btrfs: sink unlock_extent parameter gfp_flags

All callers pass either GFP_NOFS or GFP_KERNEL now, so we can sink the
parameter to the function, though we lose some of the slightly better
semantics of GFP_KERNEL in some places, it's worth cleaning up the
callchains.

Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index b8ab90c..014f3c0 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1125,8 +1125,7 @@ cleanup_write_cache_enospc(struct inode *inode,
 {
 	io_ctl_drop_pages(io_ctl);
 	unlock_extent_cached(&BTRFS_I(inode)->io_tree, 0,
-			     i_size_read(inode) - 1, cached_state,
-			     GFP_NOFS);
+			     i_size_read(inode) - 1, cached_state);
 }
 
 static int __btrfs_wait_cache_io(struct btrfs_root *root,
@@ -1320,7 +1319,7 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
 	io_ctl_drop_pages(io_ctl);
 
 	unlock_extent_cached(&BTRFS_I(inode)->io_tree, 0,
-			     i_size_read(inode) - 1, &cached_state, GFP_NOFS);
+			     i_size_read(inode) - 1, &cached_state);
 
 	/*
 	 * at this point the pages are under IO and we're happy,