rtc: ds1307: Fix incorrect clock reset for DS13xx

The ds1307 driver also supports the DS1339 and DS1340.
However, in ds1307_rtc_reset the register writes assume that the chip
is a DS1307. This is evident in the writing of bits SQWE, RS1, RS0 to
the control register. While this applies correctly to the DS1307, on a
DS1340 the control register doesn't contain those bits (instead, the
register is used for clock calibration). By writing these bits the
clock calibration will be changed and the chip can become
non-functional after a reset call.

Signed-off-by: Callum Sinclair <callum.sinclair@alliedtelesis.co.nz>