mfd: da9063: Replace model with type

The model number stored in the struct da9063 is the same for all
variants of the da9063 since it is the chip ID, which is always
the same. Replace that with a separate identifier instead, which
allows us to discern the DA9063 variants by setting the type
based on either DT match or otherwise.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Acked-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Lee Jones <lee.jones@linaro.org>