MIPS: jz4740: remove unnecessary null test before debugfs_remove

Fix checkpatch warning:
WARNING: debugfs_remove(NULL) is safe this check is probably not required

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/7225/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>