ASoC: SOF: remove unneeded variables

Remove unneeded temporary local variables and their declarations.
Change suggested by coccinelle.

Signed-off-by: Payal Kshirsagar <payalskshirsagar1234@gmail.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20200409184853.15896-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>