rtc: ds1307: add ds1308 variant

The ds1308 variant is very similar to the already supported ds1338
variant, it have more debug registers and a square wave clock output.

Signed-off-by: Sean Nyekjaer <sean.nyekjaer@prevas.dk>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
1 file changed