mmc: dw_mmc: remove _dev_info compile warning

This patch removes the following warning.
drivers/mmc/host/dw_mmc.c:1976: warning: passing argument 1 of
'_dev_info' from incompatible pointer type

Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
Acked-by: Will Newton <will.newton@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>