mmc: mmci: stm32: clear DLYB_CR after sending tuning command

mmc: mmci: stm32: clear DLYB_CR after sending tuning command

During test campaign, and especially after several unbind/bind sequences,
it has been seen that the SD-card on SDMMC1 thread could freeze.
The freeze always appear on a CMD23 following a CMD19.
Checking SDMMC internal registers shows that the tuning command (CMD19)
has failed.
The freeze is then due to the delay block involved in the tuning sequence.
To correct this, clear the delay block register DLYB_CR register after
the tuning commands.

Signed-off-by: Christophe Kerello <christophe.kerello@foss.st.com>
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Fixes: 30ecebd19740 ("mmc: mmci_sdmmc: Add execute tuning with delay block")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211215141727.4901-4-yann.gautier@foss.st.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>