extcon: standard cable names definition and declaration changed

With this change now individual drivers can use standard cable
names as below:
static const char *arizona_cable[] = {
    extcon_cable_name[EXTCON_USB],
    extcon_cable_name[EXTCON_USB_HOST],
    "CUSTOM_CABLE"
    NULL,
}

Signed-off-by: anish kumar <anish198519851985@gmail.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>