staging: binder: fix usage of uninit scalar in binder_transaction()

Fix the error path when a cookie mismatch is detected. In that case the
function jumps to the exit label without setting the uninitialized, local
variable 'return_error'. Detected by Coverity - CID 201453.
Signed-off-by: Christian Engelmayer <cengelma@gmx.at>
Acked-by: Arve <arve@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/binder.c

@@ -1547,6 +1547,7 @@ static void binder_transaction(struct binder_proc *proc,
 					proc->pid, thread->pid,
 					(u64)fp->binder, node->debug_id,
 					(u64)fp->cookie, (u64)node->cookie);
+				return_error = BR_FAILED_REPLY;
 				goto err_binder_get_ref_for_node_failed;
 			}
 			ref = binder_get_ref_for_node(target_proc, node);