ARM: dts: am33xx: add minimal l4 bus layout with control module support

This patch creates an l4_wkup interconnect for AM33xx, and moves some of
the generic peripherals under it. System control module nodes are moved
under this new interconnect also, and the SCM clock layout is changed
to use the renamed SCM node as the clock provider.

Signed-off-by: Tero Kristo <t-kristo@ti.com>