dpnaa2: announce transmit checksum support

Let the network stack know that the NIC supports checksum offloading
for the IPv4 header checksum and the TCP and UDP transport checksum.
This avoids the computation in software and therefore provides the
expected performance gain.

PR: 292006
Reviewed by: dsl, Timo Völker
Differential Revision: https://reviews.freebsd.org/D54809

(cherry picked from commit f31336b3e3146fed9cc517fef8e877c17496f9e0)