apparmor: use passed in gfp flags in aa_alloc_null()

apparmor: use passed in gfp flags in aa_alloc_null()

These allocations should use the gfp flags from the caller instead of
GFP_KERNEL.  But from what I can see, all the callers pass in GFP_KERNEL
so this does not affect runtime.

Fixes: e31dd6e412f7 ("apparmor: fix: kzalloc perms tables for shared dfas")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: John Johansen <john.johansen@canonical.com>