clk: RK808: Reduce 'struct rk808' usage

clk: RK808: Reduce 'struct rk808' usage

Reduce usage of 'struct rk808' (driver data of the parent MFD), so
that only the chip variant field is still being accessed directly.
This allows restructuring the MFD driver to support SPI based
PMICs.

Acked-by: Stephen Boyd <sboyd@kernel.org>
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/20230504173618.142075-2-sebastian.reichel@collabora.com
Signed-off-by: Lee Jones <lee@kernel.org>