ALSA: usbmixer: rename usbmixer.[ch] -> mixer.[ch]

For clearer namespace, also rename usbmixer_maps.c -> mixer_maps.c

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/Makefile b/sound/usb/Makefile
index 744024a..e7ac7f4 100644
--- a/sound/usb/Makefile
+++ b/sound/usb/Makefile
@@ -3,7 +3,7 @@
 #
 
 snd-usb-audio-objs := 	card.o \
-			usbmixer.o \
+			mixer.o \
 			mixer_quirks.o \
 			proc.o \
 			quirks.o \