Improve max brightness handling

If we can detect the directory, why don't we detect maximum as well?

Additional patch by: Matt Mower
Replace clunky /nobrightness handling

Cleanup TWFunc::Set_Brightness() and blanktimer::getBrightness() a
bit, primarily for the purpose of relying on the value in
tw_has_brightnesss_file instead of checking for a phony brightness
path.

Change-Id: Ib22595df53cefa8db7a1172a581984c42ad461c6
diff --git a/gui/blanktimer.cpp b/gui/blanktimer.cpp
index 95b6c47..06208e2 100644
--- a/gui/blanktimer.cpp
+++ b/gui/blanktimer.cpp
@@ -81,16 +81,13 @@
 
 string blanktimer::getBrightness(void) {
 	string result;
-	string brightness_path;
-	DataManager::GetValue("tw_brightness_file", brightness_path);
-	if (brightness_path == "/nobrightness")
-		return brightness_path;
-	DataManager::GetValue("tw_brightness", result);
-	if (result == "") {
-		result = "255";
+
+	if (DataManager::GetIntValue("tw_has_brightnesss_file")) {
+		DataManager::GetValue("tw_brightness", result);
+		if (result.empty())
+			result = "255";
 	}
 	return result;
-
 }
 
 void blanktimer::resetTimerAndUnblank(void) {
@@ -112,7 +109,7 @@
 			gui_forceRender();
 			// No break here, we want to keep going
 		case kDim:
-			if (orig_brightness != "/nobrightness")
+			if (!orig_brightness.empty())
 				TWFunc::Set_Brightness(orig_brightness);
 			state = kOn;
 		case kOn: