dts: arm64: ti: am62x_a53: Add mailbox nodes

Add TI OMAP interprocessor mailbox nodes for AM62X A53,
the user ID assignment is as per thec corresponding mailbox
interrupt assignment for the core. Also while at it update the
supported feature list in corresponding boards.

More details can be found in the device TRM Mailbox section:
https://www.ti.com/lit/ug/spruiv7a/spruiv7a.pdf



Signed-off-by: Vaishnav Achath <vaishnav.a@ti.com>