mmc: dw_mmc-rockchip: remove dw_mci_rockchip_pmops

dw_mci_rockchip_pmops just copy-paste what dw_mci_pltfm_pmops
have done. Let's remove it.

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>