arm: dts: sync am33xx with Linux 5.9-rc7

There have been several changes to the am33xx.dtsi, so this patch
re-syncs it with Linux.

Let's add proper interconnect hierarchy for l4 interconnect instances
with the related ti-sysc interconnect module data as documented in
Documentation/devicetree/bindings/bus/ti-sysc.txt of the Linux kernel.
With l4 interconnect hierarchy and ti-sysc interconnect target module
data in place, we can simply move all the related child devices to their
proper location and enable probing using ti-sysc.

The am33xx-clock.dtsi file is the same as that of the Linux kernel,
except for the reg property of the node l4-wkup-clkctrl@0.
As for the am33xx.dtsi file, all the devices with drivers not yet
implemented and those I was able to test with this patch have been moved
to am33xx-l4.dtsi. In case of any regressions, problem devices can be
reverted by moving them back and removing the related interconnect
target module node.

Signed-off-by: Dario Binacchi <dariobin@libero.it>