mmc: sdhci_am654: Add flag for PHY calibration

Not all controllers need calibration for the PHY DLL. Add a DLL_CALIB flag
to indicate the same.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Link: https://lore.kernel.org/r/20200619125801.9530-3-faiz_abbas@ti.com


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