ARM: dts: AM4372: Add ti,mbox-send-noirq to wkup_m3 mailbox

Add ti,mbox-send-noirq to wkup_m3 mailbox so that messages using
wkup_m3 mailbox are sent without triggering any further interrupts.
This is required to be able to send multiple messages to the WkupM3
after the mailbox usage logic adjustment in the wkup_m3_ipc driver.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Acked-by: Dave Gerlach <d-gerlach@ti.com>
[s-anna@ti.com: revise commit description]
Signed-off-by: Suman Anna <s-anna@ti.com>