mmc: mediatek: make function msdc_cqe_disable() static

mmc: mediatek: make function msdc_cqe_disable() static

The sparse tool complains as follows:

drivers/mmc/host/mtk-sd.c:2269:6: warning:
 symbol 'msdc_cqe_disable' was not declared. Should it be static?

This function is not used outside of mtk-sd.c, so this commit
marks it static.

Fixes: 88bd652b3c74 ("mmc: mediatek: command queue support")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Chun-Hung Wu <chun-hung.wu@mediatek.com>
Link: https://lore.kernel.org/r/20200727171129.2945-1-weiyongjun1@huawei.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>