Change comments for rte_flow_validate() function to indicate that flow
rule collision and resource validation is optional for PMDs and
therefore the return codes may have different meanings.
Fixes: b1a4b4cbc0 ("ethdev: introduce generic flow API")
Signed-off-by: John Daley <johndale@cisco.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>