mmc: sdhci-pci-gli: Fine tune GL9763E L1 entry delay

Fine tune the value to 21us in order to improve read/write performance.

Signed-off-by: Ben Chuang <benchuanggli@gmail.com>
Link: https://lore.kernel.org/r/20210511061835.5559-1-benchuanggli@gmail.com


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