wl1271: sdio: add suspend/resume support

Add required suspend/resume support to prevent the SDIO
core from removing our card completely during system suspend.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>