ARM: dts: imx6qdl-sr-som: update phy configuration for som revision 1.9

Since SoM revision 1.9 the PHY has been replaced with an ADIN1300,
add an entry for it next to the original.

As Russell King pointed out, additional phy nodes cause warnings like:
mdio_bus 2188000.ethernet-1: MDIO device at address 1 is missing
To avoid this the new node has its status set to disabled. U-Boot will
be modified to enable the appropriate phy node after probing.

The existing ar8035 nodes have to stay enabled by default to avoid
breaking existing systems when they update Linux only.

Co-developed-by: Alvaro Karsz <alvaro.karsz@solid-run.com>
Signed-off-by: Alvaro Karsz <alvaro.karsz@solid-run.com>
Signed-off-by: Josua Mayer <josua@solid-run.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>