usb: phy: qmp: Remove ext-vbus-id property

The QMP SSPHY will always be used in configurations
where VBUS and ID detection are handled externally,
so remove this device tree property as there is no
need to distinguish it.

Change-Id: I9cf391f0e4606369a7103134fa4bceefb7d9955a
Signed-off-by: Jack Pham <jackp@codeaurora.org>