omap2: i2c: add syss offset

OMAP2420 ES2.3 trm defines syss register offset as 0x10. Add it.

Cc: Steve Sakoman <steve@sakoman.com>
Cc: Heiko <hs@denx.de>
Cc: Sandeep Paulraj <s-paulraj@ti.com>
Cc: Wolfang Denk <wd@denx.de>

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Steve Sakoman <steve@sakoman.com>