mmc: cqhci: Fix NULL pointer dereference crash

Add a check on cmdq_host->ops to avoid NULL pointer
dereference, if sdhci_dumpregs is called before
initializing cmdq_host->ops structure.

Change-Id: Ia30cd6c008a624c6cac3b79658c647125f557b04
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>
Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>