mmc: core: Introduce MMC_CAP_SYNC_RUNTIME_PM

To allow mmc host drivers to inform the mmc core about rather using
pm_runtime_put_sync_suspend() instead of pm_runtime_put_autosuspend(),
let's introduce MMC_CAP_SYNC_RUNTIME_PM.

This is especially useful for those mmc host drivers that don't benefit
from using the runtime PM autosuspend feature. Typically this is those that
relies on parent devices to power the card via runtime PM, like some USB
host drivers for example.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>