mmc: core: Imply IOSCHED_BFQ

mmc: core: Imply IOSCHED_BFQ

If we enable the MMC/SD block layer, use Kconfig to imply the BFQ
I/O scheduler.

As all MMC/SD devices are single-queue, this is the scheduler that
users want so let's be helpful and make sure it gets
default-selected into a manual kernel configuration. It will still
need to be enabled at runtime (usually with udev scripts).

Cc: linux-block@vger.kernel.org
Cc: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230131084742.1038135-1-linus.walleij@linaro.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>