MXC: add RTCK alternate function definitions

This one adds definitions to configure RTCK pad (PE16) in primary and alternate
function. The RTCK Pin is used by one wire master controller and as JTAG Clock
return.

Signed-off-by: Luotao Fu <l.fu@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>