Wifi: Handle invalid error values from vendor HAL

The HAL shim (default implementation) expects all vendor hal functions
to return valid wifi_error values. In case the vendor hal returning a
value outside this range of values, the HAL service crashes.

This commit is to handle this type of error by defaulting to
WIFI_ERROR_UNKNOWN.

Bug: 143317834
Test: Manual
Test: Pass an invalid error code, and make sure it is properly handled
Change-Id: Ifaba8a7e4e866a2be154c9dcaeb521cd758010ee