dts: arm: ti: Add MAIN domain UARTS

M4F can use uarts from main domain of AM62. However, interrupts are not
supported.

The common main peripheral dts is kept in dts/venodor/ti to allow
sharing between arm targets (m4, r5) and arm64 targets (a53).

Signed-off-by: Ayush Singh <ayush@beagleboard.org>