mmc: msm_sdcc: Fix NULL pointer dereference in IRQ handler

If status indicates both MCI_CMDTIMEOUT and MCI_DATATIMEOUT has
occurred when handling the IRQ, MCI_CMDTIMEOUT handler ends the
pending request that cleans up the current request pointer followed
by MCI_DATATIMEOUT trying to perform similar operation causing a
NULL pointer reference. Check whether msmsdcc_request_end() has been
done before proceeding to service any status bit in the handler.

Change-Id: I26ddffae35779749102d04b5d66a8abf06d3fb6c
Signed-off-by: Sathish Ambley <sambley@codeaurora.org>