We are seeing occasional timeouts in the Tegra mmc code when
we are reading from external MMC cards. These don't seem to be
detrimental if they are handled properly.  This CL properly
clears the "normal interrupt status register" (norintsts) in
error conditions.  If we don't do this, when we come back into
mmc_send_cmd() the register will still contain status from the
last transaction.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>