Add override-leds-permission unit

Created by: peat-psuwit

THis unit change the permission of LED files under /sys/class/leds so that phablet user can also access it (and we can use the lights hal as phablet). This is the equivalent of the patch in 5.1-based Android tree [1]. However, this method requires no change in Halium Android tree and cover more files without us explicitly writing them out.

[1] https://github.com/ubports/android_system_core/commit/bd405d14f8189470baf00065f09d76fc4b45298b