regulator: add support for SY8824C regulator

SY8824C is an I2C attached single output regulator made by Silergy Corp,
which is used on several Synaptics berlin platforms to control the
power supply of the ARM cores.

Add a driver for it.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Link: https://lore.kernel.org/r/20190827163418.1a32fc48@xhacker.debian


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