ASoC: Intel: remove second duplicated assignment to pointer 'res'

The second assignment to res is identical to the previous assignment
so it is redundant and can be removed.

Cleans up clang warning:
sound/soc/intel/skylake/skl-topology.c:191:25: warning: Value stored to
'res' during its initialization is never read

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