Chip specific support will be needed in the driver to be able to
support additional chips of the same series. Add support for it
to the driver.

To simplify adding support for more chips, call identification code
from the probe function. This lets us use a single structure for common
elements of struct pmbus_driver_info, thus reducing code size as support
for more chips is added.

Cc: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>