mmc: sdhci: add IRQ wake up support

Don't disable SD Host IRQ during suspend if it is wake up source.
Enable wakeup event during suspend.

Signed-off-by: Jialing Fu <jlfu@marvell.com>
Signed-off-by: Kevin Liu <kliu5@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>