Include bits/libc-lock.h to get __libc_once_define

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Acked-by: Austin Foxley <austinf@cetoncorp.com>

libc/inet/rpc/rpc_thread.c

@@ -14,6 +14,7 @@
 #ifdef __UCLIBC_HAS_THREADS__
 
 #include <bits/libc-tsd.h>
+#include <bits/libc-lock.h>
 
 /* Variable used in non-threaded applications or for the first thread.  */
 static struct rpc_thread_variables __libc_tsd_RPC_VARS_mem;