ARC: dwmmc: Adding DesignWare MMC driver support for ARC devboards

Add the DM_MMC-compatible DesignWare MMC driver support for Synopsys
ARC devboards. It is created to switch ARC devboards to use DM_MMC.

It required information such as clocks (Bus Interface Unit clock,
Card Interface Unit clock) and SDIO bus width.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>