mmc: cmdq_hci: 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: Idd1794e162c7a53cc63504e15e6e490481f104a3
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>