watchdog: max77620: Add support for the max77714 variant

watchdog: max77620: Add support for the max77714 variant

The MAX77714 is a MFD chip whose watchdog has the same programming
procedures as the MAX77620 watchdog, but most register offsets and bit
masks are different, as well as some features.

Support the MAX77714 watchdog by adding a variant description table holding
the differences.

All the features implemented by this driver are available on the MAX77714
except for the lack of a WDTOFFC bit. Instead of using a "HAS_*" flag we
handle this by holding in the cnfg_glbl2_cfg_bits struct field the bits
(i.e. the features) to enable in the CNFG_GLBL2 register. These bits differ
among the two models. This implementation allows to avoid any conditional
code, keeping the execution flow unchanged.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>