ALSA: compress_core: Deconstify copy callback buffer

The buffer passed to the copy callback should not be const because the
copy callback can be used for capture and playback.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/soc/soc-compress.c b/sound/soc/soc-compress.c
index 29093a3..da83e56 100644
--- a/sound/soc/soc-compress.c
+++ b/sound/soc/soc-compress.c
@@ -315,7 +315,7 @@
 }
 
 static int soc_compr_copy(struct snd_compr_stream *cstream,
-			  const char __user *buf, size_t count)
+			  char __user *buf, size_t count)
 {
 	struct snd_soc_pcm_runtime *rtd = cstream->private_data;
 	struct snd_soc_platform *platform = rtd->platform;