mmc: During a switch, poll on dat0 if available and check the final status

mmc: During a switch, poll on dat0 if available and check the final status

The switch operation can sometimes make the bus unreliable, in that case
the send_status parameter should be false to indicate not to poll using
CMD13. If polling on dat0 is possible, we should use it to detect the end
of the operation.
At the end of the operation it is safe to use CMD13 to get the status of
the card. It is important to do so because the operation may have failed.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>