usb: phy-msm-usb: do not update psy type to unknown

The userspace fails to detect the power supply type
as USB if the type is unknown at bootup.
Also, since power supply class is registered as USB
type, the default type should be USB rather than
unknown.

Change-Id: Ie212037a96d6a1edb44f72ae080492bd4dd42449
Signed-off-by: choongryeol.lee <choongryeol.lee@lge.com>