mmc: sdhci-pci-gli: Reduce power consumption for GL9755

For GL9755, reduce power consumption by lowering the LFCLK and disabling
the DMACLK on low-power.

Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
Link: https://lore.kernel.org/r/20201123053702.6083-1-benchuanggli@gmail.com


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