net: tc_act: add skbedit_ptype helper functions

The tc_act header file contains an inline function that checks if an
action is changing the skb mark of a packet and a further function to
extract the mark.

Add similar functions to check for and get skbedit actions that modify
the packet type of the skb.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>