GUI: Set brightness after gr_init()

On at least one device I've tested (htc msm8960), setting the
brightness after gr_init() is necessary for the splash to show.

Note that at this point in the boot process, the settings file has
not yet been read, so tw_brightness has its default value of max
brightness. When settings are finally loaded, the correct brightness
is loaded for the GUI.

Change-Id: Ifc58c1dc80ed9e6f6b2a269a9bb6764038626c84
diff --git a/gui/gui.cpp b/gui/gui.cpp
index f8a6a73..4c2c74b 100644
--- a/gui/gui.cpp
+++ b/gui/gui.cpp
@@ -733,6 +733,7 @@
 extern "C" int gui_init(void)
 {
 	gr_init();
+	TWFunc::Set_Brightness(DataManager::GetStrValue("tw_brightness"));
 
 	// load and show splash screen
 	if (PageManager::LoadPackage("splash", TWRES "splash.xml", "splash")) {