i2c: s3c2410: move mach/regs-iic.h into i2c-s3c2410 device driver

The register definitions are only used in the driver itself.
This also removes the last dependency on plat/ includes from the
i2c driver.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>