mmc: sdhci-of-dwcmshc: reduce CIT for better performance

mmc: sdhci-of-dwcmshc: reduce CIT for better performance

CQHCI_SSC1.CIT indicates to the CQE the polling period to use for
periodic SEND_QUEUE_STATUS (CMD13) polling. Some eMMCs have only one
hardware queue, and CMD13 can only query one slot at a time for data
transmission, which cannot be processed in parallel. Modifying the
CMD13 query interval can increase the query frequency and improve
random write performance.

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>