ASoC: cht_bsw_max98090_ti: Remove unused function cht_get_codec_dai()

Looks like the function has never been used since it was added by commit
17119a46 ("ASoC: Intel: Add Cherrytrail & Braswell machine driver
cht_bsw_max98090_ti"). Removing it fixes the following warning when
building with clang:

sound/soc/intel/boards/cht_bsw_max98090_ti.c:42:35: error: unused
    function 'cht_get_codec_dai' [-Werror,-Wunused-function]

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>