fix(mediatek): switch console to runtime state before leaving BL31

We should switch console to runtime state. If we don't do this, the
state will keep boot state even we exit from BL31.

Change-Id: Id2269ccf2fdc22e0fa088c3c0365836730172233
diff --git a/plat/mediatek/common/mtk_bl31_setup.c b/plat/mediatek/common/mtk_bl31_setup.c
index 79ab29d..7c9db8b 100644
--- a/plat/mediatek/common/mtk_bl31_setup.c
+++ b/plat/mediatek/common/mtk_bl31_setup.c
@@ -166,6 +166,7 @@
 void bl31_plat_runtime_setup(void)
 {
 	mtk_init_one_level(MTK_INIT_LVL_PLAT_RUNTIME);
+	console_switch_state(CONSOLE_FLAG_RUNTIME);
 }
 
 unsigned int plat_get_syscnt_freq2(void)