mmc: tmio: fix CMD12 (STOP) handling

mmc: tmio: fix CMD12 (STOP) handling

I always anticipated this code to be not correct, but now I had a test
case to prove it. According to all documentation I have, setting the
TMIO_STOP_STP bit ever only worked during block transfers. This bit is
like manually enforcing an autocmd12 during a so far seamless transfer.
It does NOT work when the block transfer had errors. It also does NOT
work with any other cmd except block commands. For all those, CMD12 has
to be treated like any other command. So, basically, we could use this
bit only for mrq->data->stop cmds. But for these, we happily use the
autocmd12 feature using the TMIO_STOP_SEC bit. As a result, the above
bit is not useful for us and we need to treat CMD12 as a regular cmd
always. Just remove the special handling code. Note that the BSP
recognized this issue as well yet had a more cautious solution to the
problem [1]. Which is understandable but makes CMD12 handling even more
complicated.

Checked with a Renesas Salvator-X/M3-W which needed to send CMD12 when
retuning one of my SD cards.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/horms/renesas-bsp.git/commit/?id=2838a2ff8ca776f6d18b7fbbe75f3df8dd64183a

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Jan Klötzke <jan.kloetzke@preh.de>
Tested-by: Nguyen Viet Dung <dung.nguyen.aj@renesas.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>