OMAPDSS: move the creation of debugfs files

Instead of having an ugly #ifdef mess in the core.c for creating debugfs
files, add a dss_debugfs_create_file() function that the dss drivers
can use to create the debugfs files.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/video/omap2/dss/venc.c b/drivers/video/omap2/dss/venc.c
index 90b57c5..ebb6ec6 100644
--- a/drivers/video/omap2/dss/venc.c
+++ b/drivers/video/omap2/dss/venc.c
@@ -745,7 +745,7 @@
 	return 0;
 }
 
-void venc_dump_regs(struct seq_file *s)
+static void venc_dump_regs(struct seq_file *s)
 {
 #define DUMPREG(r) seq_printf(s, "%-35s %08x\n", #r, venc_read_reg(r))
 
@@ -874,6 +874,8 @@
 	if (r)
 		goto err_reg_panel_driver;
 
+	dss_debugfs_create_file("venc", venc_dump_regs);
+
 	return 0;
 
 err_reg_panel_driver: