mmc: block: Use R1 responses for stop cmds for read requests

While using open ended transmission and thus ending the transfer by
sending a stop command, we shall use R1B only for writes and R1 shall
be used for reads. Previously R1B were used in both cases.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>