mmc: core: clear 'doing_init_tune' also after failures

Reorganize the code, so that the flag is always cleared independently of
a good or bad case.

Fixes: 97a7d87e ("mmc: core: add a 'doing_init_tune' flag and a 'mmc_doing_tune' helper")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20200914112845.21855-1-wsa+renesas@sang-engineering.com


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