hwmon: (pmbus/core) Generalise pmbus get status

Add function pmbus get status that can be used to get both pmbus
specific status & regulator status

Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
...
Change in V4
- None
Changes in V3:
- Add pmbus_is_enabled function
Changes in V2:
- Add __maybe attribute for pmbus_get_status function
- Remove unrelated changes
Link: https://lore.kernel.org/r/20230301164434.1928237-2-Naresh.Solanki@9elements.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>