defconfig: sdm845: Enable EXTCON_USB_GPIO driver

Enable the extcon-usb-gpio driver which allows configuring GPIO
pins for USB VBUS and ID detection and provides notification to
USB controller driver.

Change-Id: I4c11404dbf89856bb705943e4dfc7c67a35780a3
Signed-off-by: Jack Pham <jackp@codeaurora.org>