net: lan969x: add RGMII registers

net: lan969x: add RGMII registers

Configuration of RGMII is done by configuring the GPIO and clock
settings in the HSIOWRAP target, and configuring the RGMII port devices
in the DEVRGMII target. Both targets contain registers replicated for
the number of RGMII port devices, which is two.

Add said targets and register macros required to configure RGMII.

Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Tested-by: Robert Marko <robert.marko@sartura.hr>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://patch.msgid.link/20241220-sparx5-lan969x-switch-driver-4-v5-7-fa8ba5dff732@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>