mmc: sdhci-pxav2: Remove unnecessary null pointer check

mmc: sdhci-pxav2: Remove unnecessary null pointer check

There is no need to check for a null mrq->cmd in pxav1_request_done.
mmc_request_done already assumes it's not null, and it's always called
in this path by every SDHCI driver. This was caught by Smatch.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/9ddaef2a-05bb-4fe7-98c5-da40a0813027@stanley.mountain/
Signed-off-by: Doug Brown <doug@schmorgal.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20240714155510.48880-1-doug@schmorgal.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>