ARM: dts: aspeed: Remove undocumented XDMA nodes

ARM: dts: aspeed: Remove undocumented XDMA nodes

There's no binding defined for the device, so remove it from the
devicetrees until someone has the motivation to write one.

Squash warnings such as:

 arch/arm/boot/dts/aspeed/aspeed-ast2500-evb.dtb:
 /ahb/apb@1e6e0000/xdma@1e6e7000: failed to match any schema with
 compatible: ['aspeed,ast2500-xdma']

Link: https://lore.kernel.org/r/20240802-dt-warnings-bmc-dts-cleanups-v1-4-1cb1378e5fcd@codeconstruct.com.au
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>