regulator: max5970: Drop unused structs

After splitting the max5970 into a MFD device clean the remaining
code and drop unused structs.

The struct max5970_data and enum max5970_chip_type aren't used.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Acked-by: Lee Jones <lee@kernel.org>
Link: https://patch.msgid.link/20241002125500.78278-1-patrick.rudolph@9elements.com


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