extcon: max77693: Fix inaccurate extcon event for JIG with USB cable

extcon: max77693: Fix inaccurate extcon event for JIG with USB cable

Dmitry's patch 'extcon: max77693: Force using UART~' fixes problem when
device is connected JIG with USB cable. However, with the patch, driver
sends inaccurate event "USB" even muic keeps path to UART not USB. This
would make users confused.

This patch keeps Dmitry's modification working and also bypasses signaling
event "USB" when device is connected to JIG with USB cable.

Change-Id: Ia5f3328e5b0827378178502c70cb90da48e9e3f7
Signed-off-by: Jonghwa Lee <jonghwa3.lee@samsung.com>