phy: rcar-gen3-usb2: add runtime ID/VBUS pin detection

This patch adds support for runtime ID/VBUS pin detection if
the channel 0 of R-Car gen3 is used. So, we are able to use
the channel as both host and peripheral.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>