mmc: dw_mmc: Give a good reset after we give power

We should give dw_mmc a good reset after we apply power.  On some
boards vqmmc may actually be connected to the IP block in the SoC so
it's good to reset after power comes in.

Without this we sometimes see failures enumerating cards on rk3288.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>