staging: wilc1000: added support to dynamically add/remove interfaces

Removed the use of two hardcoded interfaces and added support to
add/remove the network interfaces dynamically.
Now the driver will have single default interface with name 'wlan0' and
later other interface can be added from user space application e.g
using 'iw add' command.
Also taken care to maintain 'wilc_vif' as part of 'net_device'
private data and 'wilc' struct as 'wiphy' private data.

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