Move ICS CLK chip frequency calculation code into a common board library

We have several boards that use the same ICS307 CLK chip to drive the
System clock and DDR clock.  Move the code into a common location so we
share it.

Convert the P2020DS board as the first to use the new common ICS307
code.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Timur Tabi <timur@freescale.com>
diff --git a/board/freescale/common/Makefile b/board/freescale/common/Makefile
index df289aa..d18445b 100644
--- a/board/freescale/common/Makefile
+++ b/board/freescale/common/Makefile
@@ -42,6 +42,7 @@
 COBJS-$(CONFIG_MPC8548CDS)	+= cds_pci_ft.o
 COBJS-$(CONFIG_MPC8555CDS)	+= cds_pci_ft.o
 
+COBJS-$(CONFIG_P2020DS)		+= ics307_clk.o
 
 SRCS	:= $(SOBJS:.o=.S) $(COBJS-y:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS-y))