ASoC: zte: spdif: remove duplicate initialization of dma_data

dma_data is being initialized twice, remove the unused first
initialization and use the latter one instead.  Fixed clang warning:

"warning: Value stored to 'dma_data' during its initialization is
never read"

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mark Brown <broonie@kernel.org>