Use android standardized charger mode instead of lpm.rc

See http://review.cyanogenmod.org/#/c/77926/
Thanks to pawitp
Remove unused at* binaries

- atx doesn't seem to do anything and is a pain with SELinux
- at_distributor isn't running since forever due to missing libs

Thanks to pawitp
SELinux policies

/dev/mem is supposed be access by bkmgrd, but that is not allowed
by SELinux. (And bkmgrd isn't seem to be actually accessing it.)
Thus, the chmod is removed

Thanks to pawitp