Add SELinux policy for using userfaultfd

ART runtime will be using userfaultfd for a new heap compaction
algorithm. After enabling userfaultfd in android kernels (with SELinux
support), the feature needs policy that allows { create ioctl read }
operations on userfaultfd file descriptors.

Bug: 160737021
Test: Manually tested by exercising userfaultfd ops in ART
Change-Id: I9ccb7fa9c25f91915639302715f6197d42ef988e
10 files changed