i2c: add driver for Freescale i.MX28

Currently only supporting the PIOQUEUE-mode, because DMA-support for
this platform is not yet in mainline. When it becomes available and
support has been added to this driver, it will also be suitable for
i.MX23 and STMP3xxx.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Shawn Guo <shawn.guo@freescale.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>