staging: wilc1000: return exact error of register_netdev() from wilc_netdev_init()

Refactor wilc_netdev_init() to return the error code received from
register_netdev() during the failure condition.

Earlier discussion link
[1]. https://www.spinics.net/lists/linux-wireless/msg177304.html



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