OMAP: DSS2: DSI: Change dummy macros to inline functions

Using empty macros for performance measurement functions when DSS DEBUG
is not enabled causes an unused variable warning.

Change the empty macros to empty inline functions to remove the
warning.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/omap2/dss/dsi.c

@@ -493,9 +493,18 @@ static void dsi_perf_show(struct platform_device *dsidev, const char *name)
 			total_bytes * 1000 / total_us);
 }
 #else
-#define dsi_perf_mark_setup(x)
-#define dsi_perf_mark_start(x)
-#define dsi_perf_show(x, y)
+static inline void dsi_perf_mark_setup(struct platform_device *dsidev)
+{
+}
+
+static inline void dsi_perf_mark_start(struct platform_device *dsidev)
+{
+}
+
+static inline void dsi_perf_show(struct platform_device *dsidev,
+		const char *name)
+{
+}
 #endif
 
 static void print_irq_status(u32 status)