armv7R: dts: k3: am654: Switch DMSC TX message thread ID

armv7R: dts: k3: am654: Switch DMSC TX message thread ID

Switch from using the high priority DMSC transmit message queue used
by the secure R5 MCU island boot context to the low priority message
queue. While the change in priority is irrelevant for the current boot
architecture it however gives us access to a deeper message queue that
will allow us to buffer more messages. This is an important aspect when
sending several messages without requesting and waiting for a response
in a row which is a communication scheme used during core shutdown for
example. See AM654 TISCI User Guide for additional details.

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>