staging: wilc1000: free memory allocated for general info message from firmware

Free allocated memory for failure scenario while processing the
information message received from the firmware. Added NULL check and used
kmemdup in the flow of handling information message.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>