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

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>

security/apparmor/include/audit.h

@@ -109,7 +109,7 @@ struct apparmor_audit_data {
 	int type;
 	u16 class;
 	const char *op;
-	struct aa_label *label;
+	struct aa_label *subj_label;
 	const char *name;
 	const char *info;
 	u32 request;