MIPS: db1235: Don't use MMC_CLKGATE

As a first step in removing code for MMC_CLKGATE, MIPS db1235 defconfig
which is the only current user, shall move away from this option.

The mmc host drivers au1xmmc and jz4740_mmc, which are used on MIPS
don't support clock gating through MMC_CLKGATE, thus removing the
config option will have no effect on power save - clock gating wise.

Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Chris Ball <cjb@laptop.org>