mmc: host: factor out clearing the retune state

We have this in two places, so let's have a dedicated function. It is
also more readable.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/20210624151616.38770-4-wsa+renesas@sang-engineering.com


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