mmc: sdhci-of-dwcmshc: implement specific set_uhs_signaling

We need a different set_uhs_signaling implementation for
MMC_TIMING_MMC_HS and MMC_TIMING_MMC_HS400.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Link: https://lore.kernel.org/r/20200513182602.3636a551@xhacker.debian


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>