mmc: Revert "mmc: core: Allow mmc_start_host() synchronously detect a card"

It has turned out that some mmc host drivers were not ready to deal with
this change. Let's fix those host drivers first, then we can give this a
new try.

Fixes: 2cc83bf7

 (mmc: core: Allow mmc_start_host() synchronously detect a card)
Cc: Dennis Zhou <dennis@kernel.org>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reported-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20230630120015.363982-1-ulf.hansson@linaro.org