mmc: core: Fixup broken suspend and eMMC4.5 power off notify

This patch fixes up the broken suspend sequence for eMMC with sleep
support. Additionally it reworks the eMMC4.5 Power Off Notification
feature so it fits together with the existing sleep feature.

The CMD0 based re-initialization of the eMMC at resume is re-introduced
to maintain compatiblity for devices using sleep.

A host shall use MMC_CAP2_POWEROFF_NOTIFY to enable the Power Off
Notification feature. We might be able to remove this cap later on,
if we think that Power Off Notification always is preferred over
sleep, even if the host is not able to cut the eMMC VCCQ power.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Saugata Das <saugata.das@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>