phy: rockchip-inno-usb2: make utmi vbus configurable in DT

phy: rockchip-inno-usb2: make utmi vbus configurable in DT

Rockchip USB2 phy provides utmi_avalid and utmi_bvalid for
user to check UTMI vbus status. Generally, both of them can
reflect the vbus status correctly, and the utmi_bvalid has
higher sensitivity, so we select the utmi_bvalid to get vbus
status by default.

But some special SoCs may not provide utmi_bvalid, so we
need to select utmi_avalid in this case.

Change-Id: I0d47c2237f852cb67ebd82fe2673b2bd2e6ccce6
Signed-off-by: Wu Liang feng <wulf@rock-chips.com>