hwmon: (ad7314) Remove unused defines, and rename OFFSET to SHIFT

Remove unused defines AD7314_PD, AD7314_TEMP_SIGN, and ADT7301_TEMP_SIGN.
Rename AD7314_TEMP_OFFSET to the more appropriate AD7314_TEMP_SHIFT.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Jean Delvare <khali@linux-fr.org>