mmc: mmci: Set PROBE_PREFER_ASYNCHRONOUS

All mmc host drivers should have the asynchronous probe option enabled, but
it seems like we failed to set it for mmci, so let's do that now.

Fixes: 21b2cec6 ("mmc: Set PROBE_PREFER_ASYNCHRONOUS for drivers that existed in v4.4")
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Yann Gautier <yann.gautier@foss.st.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230612143730.210390-1-ulf.hansson@linaro.org