mmc: core: Reset the cmd timeout error stats after card detection

While probing the device, we check for SDIO first, then for SD-card
and finally for eMMC. So during the  probe, few command would get fail
with time-out error. Say for eMMC device, SDIO & SD-card specific
commands would fail. So just after card detection, clear the command
timeout error stats so that it captures actual timeout error count.

Change-Id: I099f4e44652f46228589b7f6ee9eb48d58609089
Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>