Drop unused rules for raw I/O, mknod, and block device access.

We added these rules to the kernel domain when we removed them
from unconfined to ensure that we did not break anything.  But
we have seen no uses of these rules and this matches our expectation
that any actual operations that require these permissions occurs
after switching to the init domain.

Change-Id: I6f3556a26b0f6f4e6effcb874bfc9498e7dfaa47
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>