nvidiafb: fix nvidia_bl_get_level_brightness() calc

Index: ppc-2.6/drivers/video/nvidia/nv_backlight.c
===================================================================
@@ -26,6 +26,7 @@
  */
 #define MIN_LEVEL 0x158
 #define MAX_LEVEL 0x534
+#define LEVEL_STEP ((MAX_LEVEL - MIN_LEVEL) / FB_BACKLIGHT_MAX)
 
 static struct backlight_properties nvidia_bl_data;
 

@@ -37,7 +38,7 @@
 
 	/* Get and convert the value */
 	mutex_lock(&info->bl_mutex);
-	nlevel = info->bl_curve[level] * FB_BACKLIGHT_MAX / MAX_LEVEL;
+	nlevel = MIN_LEVEL + info->bl_curve[level] * LEVEL_STEP;
 	mutex_unlock(&info->bl_mutex);
 
 	if (nlevel < 0)