arm/imx2x: new IOMUX definitions

* removed iomux-mx1-mx2.h completely
* distributes the former contents to four different files (iomux-mx1.h,
  iomux-mx21.h, iomux-mx27.h and the file iomux-mx2x.h, which is common to
  both i.MX21 and i.MX27).
* adds all documented IOMUX definitions for i.MX21 and i.MX27
* fixes a few that were wrong (PD14_AOUT_FEC_CLR, PE16_AF_RTCK).
* don't silenly include <linux/io.h>
* and fixes all collateral damage from above

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>