ASoC: Intel: Skylake: remove bogus comparison of an array with NULL

dfw_ac->params is an array not a pointer. It will never be NULL. The check
on ac->max appears sufficient.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>