mmc: host: add Coldfire esdhc support

mmc: host: add Coldfire esdhc support

This driver has been developed as a separate module starting
from the similar sdhci-esdhc-imx.c.

Reasons for a separate sdchi-esdhc-mcf driver:

- m68K architecture does not support devicetrees, so modifying
sdhci-of-esdhc.c that is devicetree-related adding platform data
seems not appropriate,
- clock-related part, has to be implemented specifically for
mcf5441x family (see esdhc_mcf_pltfm_set_clock()),
- this is a big endian cpu accessing a big endian controller,
but about sdma, this controller does not support hw swap, which
needs to be handled with specific code,
- some other minor differences but mainly to avoid risks on
tweaking inside largely used imx driver. Adding just a small
size ColdFire-specific driver, with benefits in a further less
risky maintenance.

Signed-off-by: Angelo Dureghello <angelo.dureghello@timesys.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20200518191742.1251440-3-angelo.dureghello@timesys.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>