mmc: core: Invent MMC_CAP2_FULL_PWR_CYCLE

MMC_CAP2_FULL_PWR_CYCLE shall be set by host drivers which are able to
do a complete power cycle of the card. In the eMMC case that includes
both vcc and vccq.

This CAP is providing the protocol layer with important information,
needed to take optimized decisions during card initialization and in
the suspend/resume sequence.

MMC_CAP2_POWEROFF_NOTIFY is replaced by MMC_CAP2_FULL_PWR_CYCLE, since
it makes sense to use a wider scope for it.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>