arm: dts: ti: k3-am64-main: Add RTI watchdog nodes

Add the needed bus mappings for the two main RTI memory ranges and
the required device tree nodes in the main domain.

Same as kernel commit 6dd8457dc20693e2ba9054c171499b22664fd4e7

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>