mxs: add support for 4.9 and switch over

mxs: add support for 4.9 and switch over

I did not port the regulator and power patches from Stefan Wahren
because I talked to him and he told me that work on this is currently
stalled. And since AFAIK nothing depends on these patches, leaving them
out seems reasonable.

I build minimum default configurations and run-tested them on both
I2SE Duckbill devices and Olimex Olinuxino Maxi boards successfully [1].

[1] Tested:
- debug uart is working
- boot without any obvious kernel problem
- network is coming up and data transfer is possible
- Olinuxino: USB detects a plugged-in pen drive

Signed-off-by: Michael Heimpold <mhei@heimpold.de>
[refreshed config and patches]
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>