mmc: core: Extend mmc_switch_status() to rid of __mmc_switch_status()

To simplify code, let's extend mmc_switch_status() to cope with needs
addressed in __mmc_switch_status(). Then move all users to the updated
mmc_switch_status() API and drop __mmc_switch_status() altogether.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Baolin Wang <baolin.wang7@gmail.com>
Tested-by: Ludovic Barre <ludovic.barre@st.com>
Reviewed-by: Ludovic Barre <ludovic.barre@st.com>
Link: https://lore.kernel.org/r/20200204085449.32585-4-ulf.hansson@linaro.org