net: macb: Add "mobileye,eyeq5-gem" compatible

net: macb: Add "mobileye,eyeq5-gem" compatible

Add support for the two GEM instances inside Mobileye EyeQ5 SoCs, using
compatible "mobileye,eyeq5-gem". With it, add a custom init sequence
that must grab a generic PHY and initialise it.

We use bp->phy in both RGMII and SGMII cases. Tell our mode by adding a
phy_set_mode_ext() during macb_open(), before phy_power_on(). We are
the first users of bp->phy that use it in non-SGMII cases.

The phy_set_mode_ext() call is made unconditionally. It cannot cause
issues on platforms where !bp->phy or !bp->phy->ops->set_mode as, in
those cases, the call is a no-op (returning zero). From reading
upstream DTS, we can figure out that no platform has a bp->phy and a
PHY driver that has a .set_mode() implementation:
 - cdns,zynqmp-gem: no DTS upstream.
 - microchip,mpfs-macb: microchip/mpfs.dtsi, &mac0..1, no PHY attached.
 - xlnx,versal-gem: xilinx/versal-net.dtsi, &gem0..1, no PHY attached.
 - xlnx,zynqmp-gem: xilinx/zynqmp.dtsi, &gem0..3, PHY attached to
   drivers/phy/xilinx/phy-zynqmp.c which has no .set_mode().

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20251023-macb-eyeq5-v3-5-af509422c204@bootlin.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>