uboot-imx

MX: set a common place to share code for Freescale i.MX

Up now only MX5 and MX6 can share code, because they have
a common source directory in cpu/armv7. Other not armv7
i.MX can profit of the same shared code. Move these files
into a directory accessible for all, similar to plat-mxc
in linux.

Signed-off-by: Stefano Babic <sbabic@denx.de>