mmc: sdhci-of-arasan: Add CQHCI support for arasan,sdhci-5.1

Add CQHCI initialization and implement CQHCI operations for Arasan
SDHCI variant host, namely arasan,sdhci-5.1, which is used by Rockchip
RK3399 platform.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>