ASoC: wm8978: clarify expression

cppcheck warning:

sound/soc/codecs/wm8978.c:727:57: style: Clarify calculation
precedence for '&' and '?'. [clarifyCalculation]
 enum wm8978_sysclk_src current_clk_id = clking & 0x100 ?
                                                        ^

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/20210311004332.120901-7-pierre-louis.bossart@linux.intel.com


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