mmc: dw_mmc-pltfm: use modern PM macros

mmc: dw_mmc-pltfm: use modern PM macros

Use the modern PM macros for the suspend and resume functions to be
automatically dropped by the compiler when CONFIG_PM or CONFIG_PM_SLEEP
are disabled, without having to use #ifdef guards.

When this's done, remove all variant drivers' local pm definition and
replace it with dw_mci_pltfm_pmops.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
[Ulf: Fixed conflict by dropping changes for dw_mmc-rockchip]
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>