powerpc: MPC8536DS: Remove macro CONFIG_MPC8536DS

Use CONFIG_TARGET_MPC8536DS instead.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/board/freescale/common/Makefile b/board/freescale/common/Makefile
index c131ed9..db36e53 100644
--- a/board/freescale/common/Makefile
+++ b/board/freescale/common/Makefile
@@ -49,7 +49,7 @@
 obj-$(CONFIG_TARGET_MPC8548CDS)	+= cds_pci_ft.o
 obj-$(CONFIG_MPC8555CDS)	+= cds_pci_ft.o
 
-obj-$(CONFIG_MPC8536DS)	+= ics307_clk.o
+obj-$(CONFIG_TARGET_MPC8536DS)	+= ics307_clk.o
 obj-$(CONFIG_MPC8572DS)	+= ics307_clk.o
 obj-$(CONFIG_P1022DS)		+= ics307_clk.o
 obj-$(CONFIG_P2020DS)		+= ics307_clk.o