power: Simplify display_hint_sent

Check for whether the display hint has been sent at the start
of the set_interactive() function in the common powerHAL.

This gets rid of the need to replicate the same variable in
every target-specific powerHAL that implements the
set_interactive_override() function.

Change-Id: If7dd11fcb578211f4f83847f9257232c4138ce53

power-common.c

@@ -128,6 +128,8 @@ extern void power_set_interactive_ext(int on);
 #endif
 
 void set_interactive(int on) {
+    static int display_hint_sent;
+
     if (!on) {
         /* Send Display OFF hint to perf HAL */
         perf_hint_enable(VENDOR_HINT_DISPLAY_OFF, 0);
@@ -136,6 +138,14 @@ void set_interactive(int on) {
         perf_hint_enable(VENDOR_HINT_DISPLAY_ON, 0);
     }
 
+    /**
+     * Ignore consecutive display-off hints
+     * Consecutive display-on hints are already handled
+     */
+    if (display_hint_sent && !on) return;
+
+    display_hint_sent = !on;
+
 #ifdef SET_INTERACTIVE_EXT
     power_set_interactive_ext(on);
 #endif