btrfs: tree-checker: fix bounds check in check_inode_extref()

commit e92c2941 upstream.

The parentheses for the unlikely() annotation were put in the wrong
place so it means that the condition is basically never true and the
bounds checking is skipped.

Fixes: aab9458b ("btrfs: tree-checker: add inode extref checks")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>