OMAP: DSS2: initialize dss clk sources properly

Clk sources were not initialized, leading to kernel crash, or possibly to
strange behaviour if DSI was compiled in.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>
diff --git a/drivers/video/omap2/dss/dss.c b/drivers/video/omap2/dss/dss.c
index 8254a42..5434418 100644
--- a/drivers/video/omap2/dss/dss.c
+++ b/drivers/video/omap2/dss/dss.c
@@ -590,6 +590,9 @@
 		}
 	}
 
+	dss.dsi_clk_source = DSS_SRC_DSS1_ALWON_FCLK;
+	dss.dispc_clk_source = DSS_SRC_DSS1_ALWON_FCLK;
+
 	dss_save_context();
 
 	rev = dss_read_reg(DSS_REVISION);