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/configs/nokia_rx51_defconfig b/configs/nokia_rx51_defconfig
index d0c8929..30a02e2 100644
--- a/configs/nokia_rx51_defconfig
+++ b/configs/nokia_rx51_defconfig
@@ -4,6 +4,7 @@
 CONFIG_SYS_TEXT_BASE=0x80008000
 CONFIG_NR_DRAM_BANKS=2
 CONFIG_TARGET_NOKIA_RX51=y
+# CONFIG_TI_SYSC is not set
 # CONFIG_FIT is not set
 CONFIG_BOOTDELAY=30
 CONFIG_AUTOBOOT_KEYED=y