regulator: sy8827n: Enable REGCACHE_FLAT

Enable regmap cache to reduce i2c transactions and corresponding
interrupts if regulator is accessed frequently. Since the register map
is small, we use a FLAT regmap cache.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Link: https://lore.kernel.org/r/20210803165211.3b00db29@xhacker.debian


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