mmc: dw_mmc: Fixed sdio interrupt mask bit setting bug

The sdio interrupt mask bits are arranged in [31:16].
(1 << SDMMC_INT_SDIO(slot->id))) does 16 bits left shift twice.
So this patch changes to do 16 bits left shift only one time.

Signed-off-by: Kyoungil Kim <ki0351.kim@samsung.com>
Acked-by: Shashidhar Hiremath <shashidharh@vayavyalabs.com>
Acked-by: Will Newton <will.newton@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>