Fix init error trying to access file.

Init tries to write /proc/sys/vm/min_free_order_shift but fails due to
a SELinux denial.  This gives the file a new label and gives init the
ability to write it.

Test: Build and booted Sailfish (a couple of days ago).
Change-Id: Ic93862b85c468afccff2019d84b927af9ed2a84d