arm64: dts: freescale: imx93-var-som: update eqos support for MaxLinear PHY

Variscite has updated the Ethernet PHY on the VAR-SOM-MX93 from the
ADIN1300BCPZ to the MaxLinear MXL86110, as documented in the
August 2023 revision changelog.
Link: https://variwiki.com/index.php?title=VAR-SOM-MX93_rev_changelog



Update the device tree accordingly:
- Drop the regulator node used to power the previously PHY.
- Add support for the reset line using GPIO1_IO07 with proper timings.
- Configure the PHY LEDs via the LED subsystem under /sys/class/leds/,
  leveraging the support implemented in the mxl86110 PHY driver
  (drivers/net/phy/mxl-86110.c).
  Two LEDs are defined to match the LED configuration on the Variscite
  VAR-SOM Carrier Boards:
    * LED@0: Yellow, netdev trigger.
    * LED@1: Green, netdev trigger.
- Adjust the RGMII clock pad control settings to match the updated PHY
  requirements.

These changes ensure proper PHY initialization and LED status indication
for the new MaxLinear MXL86110, improving board compatibility with the
latest hardware revision.

Signed-off-by: Stefano Radaelli <stefano.radaelli21@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>