hardware/broadcom/wlan: dhd: add missing fini interface command

Needed to fix this error in Netd init:
W/InterfaceController: error (Symbol not found) while searching for the interface command fini function

PS: This is not called on Wifi Toggle or AP mode switch

Commit:	https://github.com/CyanogenMod/android_hardware_broadcom_wlan/commit/6863a0b90384a0fcb2d6280923e942242293f1c0