ipq806x: 6.1: restore missing dts for Netgear XR450

ipq806x: 6.1: restore missing dts for Netgear XR450

In pushing and refreshing 6.1 pull request, dbac8e8819dd ("ipq806x: 6.1:
copy patches, files and config from 5.15") wasn't correctly updated and
resulted in missing the dts for Netgear XR450. This caused compilation
error with Netgear R7800 or XR500 if testing kernel version was used.

Fix this by adding back the missing dts for Netgear XR450 from kernel
5.15.

Fixes: dbac8e8819dd ("ipq806x: 6.1: copy patches, files and config from 5.15")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>