ds1307: restore hints-based configuration on FDT systems

Fall-through to non-FDT probe code if no matching device node is found.
While here, fix indentation of the switch statement.
Also, make the device description for the hints-based attachment the
same as for FDT attachment.

Fixes: 2486b446db ds1307: add support for the EPSON RX-8035SA I2C RTC