Add sepolicy for super image

- Label super partition as super_block_device

- Add rules for kernel 4.19 support for init domain

This is a set of vendor changes necessary for interworking
with kernel verison 4.19 properly.
With kernel 4.19, additional filesystem getattr operations
are performed by init for the firmware mount points.
In addition on bootup after adb remount with Android's
Dynamic Partition feature, init needs access to underlying
block devices for overlayfs mounting.  At that stage of
init, while SELinux is initialized (thus the need to add
these rules), the underlying block device nodes in tmpfs
have not yet be labeled.

Change-Id: I1f59d701e6ec73eb66a012337eab87593e1921f6