ASoC: wm8753: Remove superfluous 'codec->cache_sync = 1'

The wm8763 driver uses regmap for IO which means that codec->cache_sync is not
used. The line was added in commit d3398ff0 ('ASoC: Convert WM8753 to direct
regmap API usage'). Presumably this was meant to be regcache_mark_dirty(), but
since we already call regcache_mark_dirty() in the core when suspending the
CODEC it is safe to just remove the line.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@linaro.org>