Move mmc suspend specific operations to be executed from the .suspend
callback in the mmc bus_ops. This simplifies the mmc_suspend_host
function which is supposed to handle nothing but common suspend tasks.

Since eMMC can be considered non-removable there are no need to check
for ongoing bkops at PM_SUSPEND_PREPARE notification so remove it.
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: NChris Ball <cjb@laptop.org>