ASoC: soc-utils: Improve kerneldoc for snd_soc_tdm_params_to_bclk()

ASoC: soc-utils: Improve kerneldoc for snd_soc_tdm_params_to_bclk()

The statement that snd_soc_tdm_params_to_bclk() is equivalent to
snd_soc_params_to_bclk() if tdm_width==tdm_slots==0 is not accurate,
it is only true is slot_multiple is also <2.

However, the description of special-case behaviour in terms of pairs of
tdm_width and tdm_slot values is not particularly helpful so we might as
well take the opportunity to rework the description to say the same thing
in a simpler way. The behaviour of a pair of values is obvious from a
description of each argument. At the same time make a few edits to clarify
the rest of the description.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220815113346.3805075-1-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>