mmc: core: Validate suspend prerequisites for SDIO at SUSPEND_PREPARE

This patch moves the validation for all the suspend prerequisites to be
done at SUSPEND_PREPARE notification. Previously in the SDIO case parts
of the validation was done from mmc_suspend_host.

This patch invents a new pre_suspend bus_ops callback and implements it
for SDIO. Returning an error code from it, will mean at SUSPEND_PREPARE
notification, the card will be removed before proceeding with the
suspend sequence.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>