set audioio available var earlier. use consistent name for waveform available variable

Author: FoamyGuy

adafruit_rtttl.py

@@ -19,20 +19,18 @@
 import pwmio
 
 AUDIOIO_AVAILABLE = False
-HAVE_WAVEFORM_LIBRARY = False
+WAVEFORM_AVAILABLE = False
 try:
     import audioio
-    from adafruit_waveform import sine
-
-    HAVE_WAVEFORM_LIBRARY = True
-
     AUDIOIO_AVAILABLE = True
+    from adafruit_waveform import sine
+    WAVEFORM_AVAILABLE = True
     try:
         import audiocore
     except ImportError:
         audiocore = audioio
 except ImportError as e:
-    if not HAVE_WAVEFORM_LIBRARY:
+    if not WAVEFORM_AVAILABLE:
         raise e
 
 try: