Revert removal of and file access to /dev/exynos

Updated fix for exynos-mem exploit (for more details, see http://forum.xda-developers.com/showthread.php?p=35560095)

/dev/exynos-mem is completely removed since it can't be used anyway with 400 filerights (reverse-merged from commit f3afce06dda047135d3199555502f13b2bd3e81d)
cma: Create a tool to create checks against cma block memory spaces

Introduce a frameork to collect the device's CMA memory blocks, and
functions able to check a given memory space against the blocks to see
if the accessed space given is a valid CMA memory request.

Use this to refuse access to unauthorized addresses given to the mmap
funtions in the mem-exynos and s5p-smem char devices.

All credits to AndreiLux
Yank555.lu v1.3g config