MSCC: add board support for the Ocelots based evaluation boards

Adding the support for 2 boards sharing common code for Ocelot chip:
PCB120 and PCB123

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
diff --git a/arch/mips/mach-mscc/Kconfig b/arch/mips/mach-mscc/Kconfig
index a8cace0..fc806fc 100644
--- a/arch/mips/mach-mscc/Kconfig
+++ b/arch/mips/mach-mscc/Kconfig
@@ -79,4 +79,6 @@
 
 endchoice
 
+source "board/mscc/ocelot/Kconfig"
+
 endmenu