bionic/x86: fix one potential deadlock in __set_tls()

Fix bug:
Currently the mutex lock _tls_desc_lock is not released
when __set_thread_area() fails. That will leads to the deadlock
when __set_tls( ) is called later on.

Change-Id: Iea3267cb0659971cba7766cbc3346f6924274f86
Signed-off-by: Jin Wei <wei.a.jin@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
diff --git a/libc/arch-x86/bionic/__set_tls.c b/libc/arch-x86/bionic/__set_tls.c
index e5e43b5..7ed4b01 100755
--- a/libc/arch-x86/bionic/__set_tls.c
+++ b/libc/arch-x86/bionic/__set_tls.c
@@ -83,6 +83,7 @@
     if (rc != 0)
     {
         /* could not set thread local area */
+        pthread_mutex_unlock(&_tls_desc_lock);
         return -1;
     }