mmc: tmio: add generic hook to fixup after a completed request

Sadly, due to HW bugs, we need a callback to work around issues just
before completing the request.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20200902081812.1591-2-wsa+renesas@sang-engineering.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>