phy: renesas: rcar-gen3-usb2: enable/disable independent irqs

Since the previous code enabled/disabled the irqs both OHCI and EHCI,
it is possible to cause unexpected interruptions. To avoid this,
this patch creates multiple phy instances from phandle and
enables/disables independent irqs by the instances.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Tested-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>