staging: wilc1000: remove host_if_work() to handle TODO list issue

Remove multiplexing of command at host_if_work().
Make use of function pointer instead of command ID to track individual
work_struct separately.

Modified the handler function to take work_struct pointer as argument
and its return type is changes to void. Now prototype of 'handle_'
function is same work_struct i.e. 'void (*fun)(struct struct *)' to
register with work_queue.
Removed host_if_work() because its not required now.
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>