mips: dts: ralink: mt7621: fix some dtc warnings

Fix the dtc warnings below.

uartlite@c00: $nodename:0: 'uartlite@c00' does not match '^serial(@.*)?$'
	From schema: /home/arinc9/Documents/linux/Documentation/devicetree/bindings/serial/8250.yaml
uartlite@c00: Unevaluated properties are not allowed ('clock-names' was unexpected)
	From schema: /home/arinc9/Documents/linux/Documentation/devicetree/bindings/serial/8250.yaml
sdhci@1e130000: $nodename:0: 'sdhci@1e130000' does not match '^mmc(@.*)?$'
	From schema: /home/arinc9/Documents/linux/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
xhci@1e1c0000: $nodename:0: 'xhci@1e1c0000' does not match '^usb(@.*)?'
	From schema: /home/arinc9/Documents/linux/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
xhci@1e1c0000: compatible: ['mediatek,mt8173-xhci'] is too short
	From schema: /home/arinc9/Documents/linux/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
switch0@0: $nodename:0: 'switch0@0' does not match '^(ethernet-)?switch(@.*)?$'
	From schema: /home/arinc9/Documents/linux/Documentation/devicetree/bindings/net/dsa/mediatek,mt7530.yaml
port@1: status:0: 'off' is not one of ['okay', 'disabled', 'reserved']
	From schema: /home/arinc9/.local/lib/python3.10/site-packages/dtschema/schemas/dt-core.yaml
port@2: status:0: 'off' is not one of ['okay', 'disabled', 'reserved']
	From schema: /home/arinc9/.local/lib/python3.10/site-packages/dtschema/schemas/dt-core.yaml
port@3: status:0: 'off' is not one of ['okay', 'disabled', 'reserved']
	From schema: /home/arinc9/.local/lib/python3.10/site-packages/dtschema/schemas/dt-core.yaml

- Change "memc: syscon@5000" to "memc: memory-controller@5000".
- Change "uartlite: uartlite@c00" to "serial0: serial@c00" and remove the
aliases node.
- Remove "clock-names" from the serial0 node. The property doesn't exist on
the 8250.yaml schema.
- Change "sdhci: sdhci@1e130000" to "mmc: mmc@1e130000".
- Change "xhci: xhci@1e1c0000" to "usb: usb@1e1c0000".
- Add "mediatek,mtk-xhci" as the second compatible string on the usb node.
- Change "switch0: switch0@0" to "switch0: switch@0"
- Change "off" to "disabled" for disabled nodes.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>