dt-bindings: reset: renesas,rzg2l-usbphy-ctrl: Document RZ/G3S support

dt-bindings: reset: renesas,rzg2l-usbphy-ctrl: Document RZ/G3S support

The Renesas USB PHY hardware block needs to have the PWRRDY bit in the
system controller set before applying any other settings. The PWRRDY bit
must be controlled during power-on, power-off, and system suspend/resume
sequences as follows:
- during power-on/resume, it must be set to zero before enabling clocks and
  modules
- during power-off/suspend, it must be set to one after disabling clocks
  and modules

Add the renesas,sysc-pwrrdy device tree property, which allows the
reset-rzg2l-usbphy-ctrl driver to parse, map, and control the system
controller PWRRDY bit at the appropriate time. Along with it add a new
compatible for the RZ/G3S SoC.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>