Fix tst-aarch64-pkey to handle ENOSPC as not supported

The syscall pkey_alloc can return ENOSPC to indicate either that all
keys are in use or that the system runs in a mode in which memory
protection keys are disabled. In such case the test should not fail and
just return unsupported.

This matches the behaviour of the generic tst-pkey.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
(cherry picked from commit 60f2d6be65)

sysdeps/unix/sysv/linux/aarch64/tst-aarch64-pkey.c

@@ -55,6 +55,10 @@ do_test (void)
       if (errno == ENOSYS || errno == EINVAL)
         FAIL_UNSUPPORTED
           ("kernel or CPU does not support memory protection keys");
+      if (errno == ENOSPC)
+        FAIL_UNSUPPORTED
+          ("no keys available or kernel does not support memory"
+           " protection keys");
       FAIL_EXIT1 ("pkey_alloc: %m");
     }