[IPSEC] xfrm_user: Kill PAGE_SIZE check in verify_sec_ctx_len()

First, it warns when PAGE_SIZE >= 64K because the ctx_len
field is 16-bits.

Secondly, if there are any real length limitations it can
be verified by the security layer security_xfrm_state_alloc()
call.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/xfrm/xfrm_user.c

@@ -101,9 +101,6 @@ static inline int verify_sec_ctx_len(struct rtattr **xfrma)
 
 	uctx = RTA_DATA(rt);
 
-	if (uctx->ctx_len > PAGE_SIZE)
-		return -EINVAL;
-
 	len += sizeof(struct xfrm_user_sec_ctx);
 	len += uctx->ctx_len;