arm64: dts: ti: k3-am62a: Enable Mailbox nodes at the board level

arm64: dts: ti: k3-am62a: Enable Mailbox nodes at the board level

Mailbox nodes defined in the top-level AM62A SoC dtsi files are
incomplete and may not be functional unless they are extended with a
chosen interrupt and connection to a remote processor.

As the remote processors depend on memory nodes which are only known at
the board integration level, these nodes should only be enabled when
provided with the above information.

Disable the Mailbox nodes in the dtsi files and only enable the ones
that are actually used on a given board.

Signed-off-by: Beleswar Padhi <b-padhi@ti.com>
Tested-by: Judith Mendez <jm@ti.com>
Acked-by: Andrew Davis <afd@ti.com>
Link: https://patch.msgid.link/20250908142826.1828676-12-b-padhi@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>