cnss: Record modem power status and notify when wlan is up

FW needs to know modem power status before accessing the
shared gpio. Cnss driver is responsible for subscribing
SSR modem status and informing FW through wlan host driver.
Currently, if cnss driver receives SSR notification
while wlan is off, it discards the message, which causes
asynchrony between FW and modem.
This change is to solve the above problem by recording modem
power status in cnss when wlan is off and sending the most
recent modem power status to wlan as soon as it is turned on.

Change-Id: Ia4ee77364e402d1e6cca9dd62b8b611e9cbb760d
Signed-off-by: Yuanyuan Liu <yuanliu@codeaurora.org>
CRs-Fixed: 625634