bus: ti: add minimal sysc interconnect target driver

We can handle the sysc interconnect target module in a generic way for
many TI SoCs. Initially let's just enable domain clocks before the
children are probed.

The code is loosely based on the drivers/bus/ti-sysc.c of the Linux
kernel version 5.9-rc7.
For DT binding details see:
- Documentation/devicetree/bindings/bus/ti-sysc.txt

Signed-off-by: Dario Binacchi <dariobin@libero.it>
diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
index 0b97fc1..875bb4e 100644
--- a/drivers/bus/Makefile
+++ b/drivers/bus/Makefile
@@ -3,4 +3,5 @@
 # Makefile for the bus drivers.
 #
 
+obj-$(CONFIG_TI_SYSC)	+= ti-sysc.o
 obj-$(CONFIG_UNIPHIER_SYSTEM_BUS) += uniphier-system-bus.o