mmc: sdhci-of-arasan: Add NULL check for data field

Add NULL check for data field retrieved from of_device_get_match_data()
before dereferencing the data.
Addresses-coverity: CID 305057:Dereference null return value (NULL_RETURNS)

Signed-off-by: Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@xilinx.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/1652339993-27280-1-git-send-email-lakshmi.sai.krishna.potthuri@xilinx.com


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