MIPS: Jz4740: Add HAVE_CLK

Jz4740 supports the clock framework but doesn't have HAVE_CLK defined,
so define it!

Signed-off-by: Maurus Cuelenaere <mcuelenaere@gmail.com>
To: linux-mips@linux-mips.org
To: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/2112/
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>