mmc: dw_mmc: brackets in register access macros

Add brackets around use of the dev argument to the
mci_{read,write}{w,l,q}() macros, for extra safety.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Will Newton <will.newton@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>