xfrm: fix XFRMA_LASTUSED comment

It is a __u64, internally time64_t.

Fixes: bf825f81 ("xfrm: introduce basic mark infrastructure")
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/uapi/linux/xfrm.h

@@ -296,7 +296,7 @@ enum xfrm_attr_type_t {
 	XFRMA_ETIMER_THRESH,
 	XFRMA_SRCADDR,		/* xfrm_address_t */
 	XFRMA_COADDR,		/* xfrm_address_t */
-	XFRMA_LASTUSED,		/* unsigned long  */
+	XFRMA_LASTUSED,		/* __u64 */
 	XFRMA_POLICY_TYPE,	/* struct xfrm_userpolicy_type */
 	XFRMA_MIGRATE,
 	XFRMA_ALG_AEAD,		/* struct xfrm_algo_aead */