ARM: S3C64XX: Add clock for i2c1

The clock for i2c1 has been missing for a while, add it to the list of
clocks for the system and ensure it is initialised at startup.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>