xfrm: Allow UDP encapsulation in crypto offload control path

Unblock this limitation so that SAs with encapsulation specified
can be passed to HW drivers. HW drivers can still reject the SA
in their implementation of xdo_dev_state_add if the encapsulation
is not supported.

Test: Verified on Android device
Signed-off-by: Mike Yu <yumike@google.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>