mmc: sdhci: Reset cmd err only for sbc commands

The data complete interrupt is also used to indicate that a
busy state has ended. Fix a race condition between sdhci_cmd_irq()
that sets any cmd err and sdhci_data_irq() (received to indicate
end of busy state) that clears cmd error. This can happen when a
cmd err is set and finish tasklet is scheduled but sdhci_data_irq()
executes before the tasklet. The cmd err status is critical for the
tasklet handler to reset the controller's state machine. This
should be cleared only when we have successfully processed a sbc
command and are ready to submit the actual command next, not when
there is an actual cmd err.

CRs-fixed: 733074
Change-Id: I91ea2b949c34446fb629446aabb21505734e27bb
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>