ALSA: oxfw: remove a meaningless entry from firewire Makefile

A former commit moves oxfw-related codes to a sub-directory, while it
forgot to remove an entry from Makefile in parent directory.

Fixes: 1a4e39c2('ALSA: oxfw: Move to its own directory')
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/Makefile

 snd-firewire-lib-objs := lib.o iso-resources.o packets-buffer.o \
 			 fcp.o cmp.o amdtp-stream.o amdtp-am824.o
-snd-oxfw-objs := oxfw.o
 snd-isight-objs := isight.o
 snd-scs1x-objs := scs1x.o