bfqio: Remove redundant extern

* This is the exported header for libbfqio, of course it includes the
  function listed. No need for extern.

Change-Id: Idbdd9b51f14e52741fed5eb7d7fb78a46bb7dc72

libbfqio/include/bfqio/bfqio.h

@@ -21,7 +21,7 @@
 extern "C" {
 #endif
 
-extern int android_set_rt_ioprio(int pid, int rt);
+int android_set_rt_ioprio(int pid, int rt);
 
 #ifdef __cplusplus
 }