ARM: mx5: move to a standard arch/board approach

Move the MX5 based boards to arch/arm/cpu/armv7/mx5, following the
commit: 89ebc821

Signed-off-by: Andrej Rosano <andrej@inversepath.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Vagrant Cascadian <vagrant@debian.org>
Tested-by: Chris Kuethe <chris.kuethe@gmail.com>