mmc: sdhci-of-arasan: Check return value of non-void funtions

At a couple of places, the return values of the non-void functions were
not getting checked. This was reported by the coverity tool. Modify the
code to check the return values of the same.

Addresses-Coverity: ("check_return")
Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/1623753837-21035-5-git-send-email-manish.narani@xilinx.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>