net: prp: add supervision frame generation utility function

Add support for generation of PRP supervision frames. For PRP,
supervision frame format is similar to HSR version 0, but have
a PRP Redundancy Control Trailer (RCT) added and uses a different
message type, PRP_TLV_LIFE_CHECK_DD. Also update
is_supervision_frame() to include the new message type used for
PRP supervision frame.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>