ASoC: ti: davinci-i2s: Remove the unused clk_input_pin attribute

The clk_input_pin attribute of davinci_mcbsp_dev struct is not set since
commit 257ade78 ("ASoC: davinci-i2s: Convert to use edma-pcm").

Remove the attribute.
Keep the behaviour of the MCBSP_CLKR case as MCBSP_CLKR == 0.
I can't test the BC_FP format so I added back the initial comment that
was removed by commit ec637553

 ("ASoC: DaVinci: Added selection of
clk input pin for McBSP"). This was the last dependency to
linux/platform_data/davinci_asp.h so it is not included anymore.

Remove the enum mcbsp_clk_input_pin from davinci_asp.h as it is not used
anywhere else.

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Link: https://msgid.link/r/20240402071213.11671-4-bastien.curutchet@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>