usb: musb: sunxi: Uses the resource-managed extcon API when registering extcon notifier

This patch just uses the resource-managed extcon API when registering
the extcon notifier.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>