mmc: dw_mmc: minor cleanup for dw_mci_adjust_fifoth

msize and rx_wmark are properly initialized, we dont't
need to assign them again.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>