SurfaceFlinger: rename use_smart_90_for_video flag

Rename use_smart_90_for_video -> use_content_detection_for_refresh_rate
to better describe what it controls.

Test: Play video and observe the refresh rate
Change-Id: I5ae03073bd670d0b3bc7f2861cbf3ec0d28efbe7
diff --git a/services/surfaceflinger/SurfaceFlingerProperties.h b/services/surfaceflinger/SurfaceFlingerProperties.h
index e394cca..440df49 100644
--- a/services/surfaceflinger/SurfaceFlingerProperties.h
+++ b/services/surfaceflinger/SurfaceFlingerProperties.h
@@ -81,7 +81,7 @@
 
 int32_t set_display_power_timer_ms(int32_t defaultValue);
 
-bool use_smart_90_for_video(bool defaultValue);
+bool use_content_detection_for_refresh_rate(bool defaultValue);
 
 bool enable_protected_contents(bool defaultValue);