libtimeinstate: export cputimeinstate.h

Make the definitions in cputimeinstate.h available to this library's
users.

Test: build now succeeds after adding libtimeinstate as a dependency
in other projects
Bug: 138317993
Signed-off-by: Connor O'Brien <connoro@google.com>

Change-Id: I1148ab4e4f3492b723279a71f3c96c70e5c92f4e
diff --git a/libs/cputimeinstate/Android.bp b/libs/cputimeinstate/Android.bp
index a8f7d92..b1943a4 100644
--- a/libs/cputimeinstate/Android.bp
+++ b/libs/cputimeinstate/Android.bp
@@ -14,6 +14,7 @@
         "-Wall",
         "-Wextra",
     ],
+    export_include_dirs: ["."],
 }
 
 cc_test {