rsi: sdio: Add WOWLAN support for S5 shutdown state

Unlike other power states, WoWLAN configuration does not come from
mac80211 for shutdown. Hence configuring the WoWLAN from shut down
callback it self. Remaining steps of disabling SDIO interrupts,
setting 'MMC_PM_KEEP_POWER' flag are same as other power states.

Signed-off-by: Karun Eagalapati <karun256@gmail.com>
Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>