Whenever the WCN3990 firmware becomes unavailable,
the host driver receives a FW down indication, post
which all the direct hardware register access should
be avoided, in order to prevent improper behavior in
the host driver.

Set the crash_flush flag when the host driver receives
a FW_DOWN_IND via qmi, in order to stop the untimely
hardware register access. Also handle the case, where
we need to do core register only for the first FW_READY
indication, which is when we initialize the host driver.
All the subsequent FW_READY indication will be received
in subsystem recovery case and we only need to do the
restart work. The state of driver is maintained using
flags to distinguish between first and subsequent FW_READY
indication received.

Tested HW: WCN3990
Tested FW: WLAN.HL.2.0-01188-QCAHLSWMTPLZ-1
Signed-off-by: Surabhi Vishnoi <svishnoi@codeaurora.org>
Signed-off-by: Rakesh Pillai <pillair@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>