usb: cdns3-starfive: Add extcon usb gadget state with always connected

usb: cdns3-starfive: Add extcon usb gadget state with always connected

Add extcon usb gadget state and set usb gadget state as connected.

The cdns3-starfive usb c port in visionfive2 board only has usb
d-/d+ lines and vbus and ground lines are used for power supply.
Because of the H/W limitation, it is not possible to detect usb
c port connected state.

In Tizen, deviced configures usb gadget functions only with the
usb connected state, so, to support usb gadget functionality,
the usb state should be set.

Change-Id: Ib951c105e3e8dfe5d1a2f0b921dabe6a7a8d61bc
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>