mmc: dw_mmc: move pmops into core driver

mmc: dw_mmc: move pmops into core driver

Since the platform power management structure is now shared with the PCI
front-end, there is a link failure if only the PCI variant is enabled:

arm-linux-gnueabi/bin/arm-linux-gnueabi-ld: drivers/mmc/host/dw_mmc-pci.o:(.data+0x74): undefined reference to `dw_mci_pltfm_pmops'

This could be fixed by selecting the platform driver from the PCI one
in Kconfig, or by reverting the change to the PCI driver, but since this
is now used by all dw_mmc variants, just move the structure into the core
code as well.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>