ASoC: wm8903: remove useless assignments

cppcheck warnings:

sound/soc/codecs/wm8903.c:1552:11: style: Variable 'best_val' is
assigned a value that is never used. [unreadVariable]
 best_val = ((clk_sys * 10) / bclk_divs[0].ratio) - bclk;
          ^
sound/soc/codecs/wm8903.c:1559:12: style: Variable 'best_val' is
assigned a value that is never used. [unreadVariable]
  best_val = cur_val;
           ^

Indeed what matters in the code is the blck_div, the best_val is
assigned but never tested or used.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20210311004332.120901-5-pierre-louis.bossart@linux.intel.com


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