drivers: wifi: Fix crash when recovery is triggered

There is a race condition when recovery is in progress and in parallel
Wi-Fi util commands are being executed (CTF), where the RPU context is
de-initialized as part of recovery but no checks are present in the
Wi-Fi util command processing causing a crash.

This needs a proper fix for all commands, but for maintenance branch
fix is added only for commonly used commands.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>