powerpc/mpc5121: Add generic board support for MPC5121 platforms

Move shared code from mpc5121_ads.c to new file mpc512x_shared.c
- mpc512x_find_ips_freq -> unchanged
- contents of mpc5121_ads_init_IRQ -> mpc512x_init_IRQ
  - looking for fsl,mpc5121-ipic instead of fsl,ipic
- mpc5121_ads_declare_of_platform_devices -> mpc5121_declare_of_platform_devices
  - and use compatible for lookup instead of node name

Add new generic board setup mpc5121_generic.c

Signed-off-by: John Rigby <jrigby@freescale.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/arch/powerpc/platforms/512x/Kconfig b/arch/powerpc/platforms/512x/Kconfig
index 162af06..5d72dc34 100644
--- a/arch/powerpc/platforms/512x/Kconfig
+++ b/arch/powerpc/platforms/512x/Kconfig
@@ -3,12 +3,10 @@
 	select FSL_SOC
 	select IPIC
 	select PPC_CLOCK
-	default n
 
 config PPC_MPC5121
 	bool
 	select PPC_MPC512x
-	default n
 
 config MPC5121_ADS
 	bool "Freescale MPC5121E ADS"
@@ -17,4 +15,15 @@
 	select PPC_MPC5121
 	help
 	  This option enables support for the MPC5121E ADS board.
-	default n
+
+config MPC5121_GENERIC
+	bool "Generic support for simple MPC5121 based boards"
+	depends on PPC_MULTIPLATFORM && PPC32
+	select DEFAULT_UIMAGE
+	select PPC_MPC5121
+	help
+	  This option enables support for simple MPC5121 based boards
+	  which do not need custom platform specific setup.
+
+	  Compatible boards include:  Protonic LVT base boards (ZANMCU
+	  and VICVT2).