mmc: dw_mmc: Don't loop when handling an interrupt

There is no reason to loop when handling an interrupt. The "if" clauses
will handle all of them sequentially. This also eliminates the extra loop
we used to take with no pending interrupts and we ended up breaking out
of the while loop.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: Seungwon Jeon <tgih.jun@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>