cpufreq: mediatek-hw: Refactor match data into struct

cpufreq: mediatek-hw: Refactor match data into struct

While the driver could get away with having the per-compatible match
data just be an array of the reg offsets, the only thing it used it for
right now, this doesn't really allow it to be extended in any meaningful
way if some other per-variant information needs to be communicated.

In preparation of adding support for hybrid "FDVFS" for MT8196, refactor
the code to make the DT match data a struct, which currently only
contains a single member: the reg offsets. This will allow this struct
to be extended with other members for other hardware variants.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>