reset: microchip-sparx5: issue a reset on startup

Originally this was used in by the switch core driver to issue a reset.
But it turns out, this isn't just a switch core reset but instead it
will reset almost the complete SoC.

Instead of adding almost all devices of the SoC a shared reset line,
issue the reset once early on startup. Keep the reset controller for
backwards compatibility, but make the actual reset a noop.

Suggested-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Michael Walle <michael@walle.cc>
Tested-by: Steen Hegelund <Steen.Hegelund@microchip.com> on Sparx5
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20220826115607.1148489-2-michael@walle.cc