alsa-mixer: Fix a git-am cockup in b0f72311

It seems git managed to mess up a git-am with a patch from
David which moved where this function was called element_probe
to within itself (recursive which could normally lead to an
infinite loop, but as it was now never called from anywhere else,
this didn't happen).

Thank you to Maarten for spotting and following up the issue.

src/modules/alsa/alsa-mixer.c

@@ -1154,9 +1154,6 @@ static int check_required(pa_alsa_element *e, snd_mixer_elem_t *me) {
         }
     }
 
-    if (check_required(e, me) < 0)
-        return -1;
-
     return 0;
 }
 
@@ -1360,6 +1357,9 @@ static int element_probe(pa_alsa_element *e, snd_mixer_t *m) {
         }
     }
 
+    if (check_required(e, me) < 0)
+        return -1;
+
     return 0;
 }