ASoC: fsl_micfil: Drop unused register read

In get_pdm_clk() REG_MICFIL_CTRL2 is read, but the result is never used.
Drop the unused code.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Shengjiu Wang <shengjiu.wang@gmail.com>
Link: https://lore.kernel.org/r/20220414162249.3934543-3-s.hauer@pengutronix.de


Signed-off-by: Mark Brown <broonie@kernel.org>