mfd: rk808: Replace 'struct i2c_client' with 'struct device'

mfd: rk808: Replace 'struct i2c_client' with 'struct device'

Put 'struct device' pointer into the MFD platform_data instead
of the 'struct i2c_client' pointer. This simplifies the code
and prepares the MFD for SPI support.

Tested-by: Diederik de Haas <didi.debian@cknow.org> # Rock64, Quartz64 Model A + B
Tested-by: Vincent Legoll <vincent.legoll@gmail.com> # Pine64 QuartzPro64
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20230504173618.142075-5-sebastian.reichel@collabora.com
Signed-off-by: Lee Jones <lee@kernel.org>