ASoC: fsl: Remove fsl_asoc_xlate_tdm_slot_mask()

Now that the fsl DAI drivers uses the same semantics as the rest of a ASoC
the custom fsl_asoc_xlate_tdm_slot_mask() callback can be removed as it is
identical to the generic one.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>