xfrm: bring back device check in validate_xmit_xfrm

This is partial revert of commit d53dda29.

This change causes traffic using GSO with SW crypto running through a
NIC capable of HW offload to no longer get segmented during
validate_xmit_xfrm, and is unrelated to the bonding use case mentioned
in the commit.

Fixes: d53dda29 ("xfrm: Remove unneeded device check from validate_xmit_xfrm")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>