ASoC: Intel: avs: Remove unused variable

ASoC: Intel: avs: Remove unused variable

Recent commit removed the only user of bus variable in
avs_dai_fe_prepare(), also remove the variable itself.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202309292121.5DdaNpLj-lkp@intel.com/
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Link: https://lore.kernel.org/r/20231002084629.903103-1-amadeuszx.slawinski@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>