MIPS: Ci20: Enable GPIO driver

Update the Ci20's defconfig to enable the JZ4780's GPIO driver.

Signed-off-by: Harvey Hunt <harvey.hunt@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16751/


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