ASoC: Intel: Skylake: Fix the NHLT rate size

Sampling rate type needs to be u32 instead of u8, nhlt wav format
description expected u32 for rate, passing u8 will fetch NULL
config in skl_get_ep_blob().

Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>