apparmor: rename audit_data->label to audit_data->subj_label

apparmor: rename audit_data->label to audit_data->subj_label

[ Upstream commit d20f5a1a6e792d22199c9989ec7ab9e95c48d60c ]

rename audit_data's label field to subj_label to better reflect its
use. Also at the same time drop unneeded assignments to ->subj_label
as the later call to aa_check_perms will do the assignment if needed.

Reviewed-by: Georgia Garcia <georgia.garcia@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Stable-dep-of: 157a3537d6bc ("apparmor: Fix regression in mount mediation")
Signed-off-by: Sasha Levin <sashal@kernel.org>