rtc: ds1307: Drop of_match_ptr and CONFIG_OF protections

These prevent use of this driver with ACPI via PRP0001.
Drop them to remove this restriction.

Also added mod_devicetable.h include given use of struct of_device_id.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201116142859.31257-3-andriy.shevchenko@linux.intel.com