mmc: sdhci-of-arasan: Allow configuring zero tap values

Allow configuring the Output and Input tap values with zero to avoid
failures in some cases (one of them is SD boot mode) where the output
and input tap values may be already set to non-zero.

Fixes: a5c8b2ae ("mmc: sdhci-of-arasan: Add support for ZynqMP Platform Tap Delays Setup")
Signed-off-by: Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@xilinx.com>
Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/1605515565-117562-2-git-send-email-manish.narani@xilinx.com


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