arm64: dts: imx8dxl-ss-conn: Disable USB3 nodes

The i.MX 8DualXLite/8SoloXLite has a different connectivity memory map
than the generic i.MX8 has.  One conflicting resource is usb, where the
imx8dxl has a second usb2 phy @5b110000, while the generic imx8 dtsi has
one usb2 phy and one usb3 phy, and the usb3otg @5b110000.  When
including both imx8dxl-ss-conn.dtsi and imx8-ss-conn.dtsi as done in
imx8dxl.dtsi this leads to a duplicate unit-address warning.

The usb3otg node was introduced after the initial imx8dxl support with
commit a8bd7f15 ("arm64: dts: imx8qxp: add cadence usb3 support")
and since then leads to warnings like this (when built with W=2):

      DTC     arch/arm64/boot/dts/freescale/imx8dxl-evk.dtb
    …/arch/arm64/boot/dts/freescale/imx8-ss-conn.dtsi:148.24-182.4: Warning (unique_unit_address): /bus@5b000000/usb@5b110000: duplicate unit-address (also used in node /bus@5b000000/usbphy@5b110000)
      also defined at …/arch/arm64/boot/dts/freescale/imx8dxl-ss-hsio.dtsi:41.23-50.4
      also defined at …/arch/arm64/boot/dts/freescale/imx8dxl-evk.dts:645.8-653.3

Delete usb3 related nodes at dxl to fix above warning.

Signed-off-by: Alexander Dahl <ada@thorsis.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>