As per RZ/G2L HW manual, VBUS enable can be controlled by the VBOUT bit
of the VBUS Control Register(VBENCTL) register in the USBPHY Control.

Expose this register as regmap and instantiate the USB VBUS regulator
device, so that consumer can control the vbus using regulator API's
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20240702180032.207275-3-biju.das.jz@bp.renesas.comSigned-off-by: Philipp Zabel <p.zabel@pengutronix.de>