staging: wilc1000: remove function pointer cfg_init

This patch removes function pointer cfg_init and call the function
wilc_wlan_cfg_init instead. Remove static from function declaration.
After removing cfg_init, the struct wilc_cfg_func_t is useless so just delete
it and it's related codes.

Signed-off-by: Glen Lee <glen.lee@atmel.com>
Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>