ASoC: SSM2602: Add entry for the ssm2603 to the device id table

The SSM2603 is mostly register compatible with the SSM2602 and can be supported
by the current driver without any changes.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>