mfd: bd9571mwv: Make the driver more generic

Since the driver supports BD9571MWV PMIC only, this patch makes
the functions and data structure become more generic so that
it can support other PMIC variants as well. Also remove printing
part name which Lee Jones suggested.

Signed-off-by: Khiem Nguyen <khiem.nguyen.xt@renesas.com>
Co-developed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Acked-for-MFD-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>