ALSA: sparc: Fix invalid snd_free_pages() at error path

Some spurious calls of snd_free_pages() have been overlooked and
remain in the error paths of sparc cs4231 driver code.  Since
runtime->dma_area is managed by the PCM core helper, we shouldn't
release manually.

Drop the superfluous calls.

Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>