Met randomly switch fail (60%) on 8QXP ARM2 A1 board, when entering eMMC HS200 or SD SDR104 mode.
The failure happens on the first command (CMD55 for SD,  CMD8 for eMMC) after the tuning process
is done.  The failure error is CTOE (command timeout).  Can't reproduce it on QXP MEK.

This patch addes a workaround to send CMD12 after tuning process is done.  This helps to stop any
transmission that device may involve during tuning. The stress test is passed on QXP ARM A1 with
this workaround added.

Also this patch fixes a issue for tuning parameter "tuning_start_tap".

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>