ALSA: compress_offload: Use runtime pointer in snd_compr_poll()

ALSA: compress_offload: Use runtime pointer in snd_compr_poll()

runtime is not used as seen with W=1 :
sound/core/compress_offload.c: In function ‘snd_compr_poll’:
sound/core/compress_offload.c:409:35: error: variable ‘runtime’ set but not used [-Werror=unused-but-set-variable]
  409 |         struct snd_compr_runtime *runtime;
      |                                   ^~~~~~~

Instead of dropping the runtime, use it in the function in place of
stream->runtime

Fixes: 04177158cf98 ("ALSA: compress_offload: introduce accel operation mode")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://patch.msgid.link/20241106075312.15601-1-peter.ujfalusi@linux.intel.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>