net: check fragmented headers in non-debug as well

net: check fragmented headers in non-debug as well

Pseudo-header checksum calculation requires contiguous headers.
There is no any formal requirements on data location and mbuf
structure which could be used by the application.

Since

commit dfc6b2fd8da3 ("mbuf: remove Intel offload checks from generic API")

fragmented headers checks are done inside
rte_net_intel_cksum_flags_prepare() in RTE_LIBRTE_ETHDEV_DEBUG build
because it is moved from rte_validate_tx_offload() which is called
under debug only.

Make corresponding check to be done in non-debug build as well
to avoid bad accesses, incorrect checksum calculation and to
return appropriate error from Tx prepare.

Make no-offloads check more precise and do it in non-debug build
as well to avoid contiguous headers check and Tx prepare failure
if it is not actually required.

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>