xtensa: add ret_ERRVAL definition

ret_ERRVAL is used by mq_timedsend and mq_timedreceive, it needs to be
defined to retw, otherwise error return from those functions segfaults.

This fixes the following testsuite failures:

  .... tst-mqueue1
  FAIL tst-mqueue1 got 1 expected 0
  	Didn't expect signal from child: got `Segmentation fault'
  .... tst-mqueue2
  FAIL tst-mqueue2 got 1 expected 0
  	Didn't expect signal from child: got `Segmentation fault'
  .... tst-mqueue3
  FAIL tst-mqueue3 got 1 expected 0
  	Didn't expect signal from child: got `Segmentation fault'
  .... tst-mqueue4
  FAIL tst-mqueue4 got 1 expected 0
  	Didn't expect signal from child: got `Segmentation fault'
  .... tst-mqueue5
  FAIL tst-mqueue5 got 1 expected 0
  	Didn't expect signal from child: got `Segmentation fault'
  .... tst-mqueue6
  FAIL tst-mqueue6 got 1 expected 0
  	Didn't expect signal from child: got `Segmentation fault'

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

libc/sysdeps/linux/xtensa/sysdep.h

@@ -132,6 +132,9 @@
 #define	PSEUDO_END_ERRVAL(name)						      \
   END (name)
 
+#undef	ret_ERRVAL
+#define ret_ERRVAL retw
+
 #if defined _LIBC_REENTRANT
 # if defined USE___THREAD
 #  ifndef NOT_IN_libc