OMAPDSS: separate compat files in the Makefile

Separate the core DSS files and compat layer files in the Makefile for
clarity.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/omap2/dss/Makefile

 obj-$(CONFIG_OMAP2_DSS) += omapdss.o
+# Core DSS files
 omapdss-y := core.o dss.o dss_features.o dispc.o dispc_coefs.o display.o \
-	manager.o manager-sysfs.o overlay.o overlay-sysfs.o output.o apply.o \
-	display-sysfs.o dispc-compat.o
+	output.o
+# DSS compat layer files
+omapdss-y += manager.o manager-sysfs.o overlay.o overlay-sysfs.o apply.o \
+	dispc-compat.o display-sysfs.o
 omapdss-$(CONFIG_OMAP2_DSS_DPI) += dpi.o
 omapdss-$(CONFIG_OMAP2_DSS_RFBI) += rfbi.o
 omapdss-$(CONFIG_OMAP2_DSS_VENC) += venc.o venc_panel.o