ARM: i.MX51 iomux: added missing pin definitions

This patch adds missing definitions for DISP, GPT and CCM pads.
These pins are not used by kernel, but may be helpful for custom boards.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>