mmc: dw_mmc: reset FIFO after an error

If an error occurs mid way through a transaction (such as a missing CRC
status response after the 2nd block written out of 3), then the FIFO may
still contain data which will interfere with the next transaction.
Therefore after an error has been detected, reset the fifo using the
CTRL register.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Will Newton <will.newton@imgtec.com>
Tested-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>