ARM: dts: am4372: Mark omap_l3_noc with ti,no-idle

We can never idle the l3_main hwmod so mark the omap_l3_noc node
with ti,no-idle.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>