selinux: do not allocate hashtabs dynamically

It is simpler to allocate them statically in the corresponding
structure, avoiding unnecessary kmalloc() calls and pointer
dereferencing.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
[PM: manual merging required in policydb.c]
Signed-off-by: Paul Moore <paul@paul-moore.com>