usb: common: usb-conn-gpio: fix NULL pointer dereference of charger

When power on system with OTG cable, IDDIG's interrupt arises before
the charger registration, it will cause a NULL pointer dereference,
fix the issue by registering the power supply before requesting
IDDIG/VBUS irq.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1621406386-18838-1-git-send-email-chunfeng.yun@mediatek.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>