ALSA: sh: Fix unused variable warnings

Remove unused variables that are left over after the conversion of new
PCM ops:
  sound/sh/sh_dac_audio.c:166:26: warning: unused variable 'runtime'
  sound/sh/sh_dac_audio.c:186:26: warning: unused variable 'runtime'
  sound/sh/sh_dac_audio.c:205:26: warning: unused variable 'runtime'

Fixes: 1cc2f8ba ("ALSA: sh: Convert to the new PCM ops")
Link: https://lore.kernel.org/r/20200104110057.13875-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>