thermal: Add AThermal_getThermalHeadroom

Bug: b/168612028
Change-Id: I8f192b50f74b1666beeab3ad546c9e3b25842187
diff --git a/native/android/libandroid.map.txt b/native/android/libandroid.map.txt
index eca67bd..569a407 100644
--- a/native/android/libandroid.map.txt
+++ b/native/android/libandroid.map.txt
@@ -291,6 +291,7 @@
     AThermal_getCurrentThermalStatus; # introduced=30
     AThermal_registerThermalStatusListener; # introduced=30
     AThermal_unregisterThermalStatusListener; # introduced=30
+    AThermal_getThermalHeadroom; # introduced=31
   local:
     *;
 };