OMAPDSS: Add enum dss_pll_id

In some cases we need global identifiers for the DSS PLLs, for example
when configuring clock muxing on DRA7. For this purpose let's add a
'enum dss_pll_id'.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/video/fbdev/omap2/dss/dss.h b/drivers/video/fbdev/omap2/dss/dss.h
index 14fb0c2..1826ee9 100644
--- a/drivers/video/fbdev/omap2/dss/dss.h
+++ b/drivers/video/fbdev/omap2/dss/dss.h
@@ -100,6 +100,12 @@
 	DSS_WB_LCD3_MGR =	7,
 };
 
+enum dss_pll_id {
+	DSS_PLL_DSI1,
+	DSS_PLL_DSI2,
+	DSS_PLL_HDMI,
+};
+
 struct dss_pll;
 
 #define DSS_PLL_MAX_HSDIVS 4
@@ -150,6 +156,7 @@
 
 struct dss_pll {
 	const char *name;
+	enum dss_pll_id id;
 
 	struct clk *clkin;
 	struct regulator *regulator;