mmc: android-goldfish: Enable MMC_CAP2_NO_SDIO

Instead of explicitly checking for SDIO specific requests and then
returning an error code, let's set MMC_CAP2_NO_SDIO to tell the mmc core to
prevent them altogether.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20200401145531.23247-1-ulf.hansson@linaro.org