btrfs: simplify error check condition at btrfs_dirty_inode()

The following condition at btrfs_dirty_inode() is redundant:

  if (ret && (ret == -ENOSPC || ret == -EDQUOT))

The first check for a non-zero 'ret' value is pointless, we can simplify
this to simply:

  if (ret == -ENOSPC || ret == -EDQUOT)

Not only this makes it easier to read, it also slightly reduces the text
size of the btrfs kernel module:

  $ size fs/btrfs/btrfs.ko.before
     text	   data	    bss	    dec	    hex	filename
  1641400	 168265	  16864	1826529	 1bdee1	fs/btrfs/btrfs.ko.before

  $ size fs/btrfs/btrfs.ko.after
     text	   data	    bss	    dec	    hex	filename
  1641224	 168181	  16864	1826269	 1bdddd	fs/btrfs/btrfs.ko.after
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -6011,7 +6011,7 @@ static int btrfs_dirty_inode(struct btrfs_inode *inode)
 		return PTR_ERR(trans);
 
 	ret = btrfs_update_inode(trans, root, inode);
-	if (ret && (ret == -ENOSPC || ret == -EDQUOT)) {
+	if (ret == -ENOSPC || ret == -EDQUOT) {
 		/* whoops, lets try again with the full transaction */
 		btrfs_end_transaction(trans);
 		trans = btrfs_start_transaction(root, 1);