Remove deprecated UNUSED macro (5/5)

Include osi.h for UNUSED_ATTR.

Test: mma -j32

Change-Id: I43260669dc1f54639e46cc9620093d727ee86276
diff --git a/stack/btm/btm_pm.cc b/stack/btm/btm_pm.cc
index 18b2693..312baf6 100644
--- a/stack/btm/btm_pm.cc
+++ b/stack/btm/btm_pm.cc
@@ -45,6 +45,7 @@
 #include "hcimsgs.h"
 #include "l2c_int.h"
 #include "osi/include/log.h"
+#include "osi/include/osi.h"
 
 /*****************************************************************************/
 /*      to handle different modes                                            */