net/failsafe: fix default Tx offloads capabilities

net/failsafe: fix default Tx offloads capabilities

Failsafe reported Tx offloads capabilities are the AND result of its
default capabilities and those of its sub-devices.
In the corrupted code failsafe default Tx capabilities were set to 0.
As a result when running testpmd with "--tx-offloads=0x8000" parameter
(request for multi segments offload) - an error was returned:

PMD: net_failsafe:
Some Tx offloads are not supported, requested 0x8000 supported 0x0

To fix this, failsafe default Tx offload capabilities are set to
DEV_TX_OFFLOAD_MULTI_SEGS |
DEV_TX_OFFLOAD_IPV4_CKSUM |
DEV_TX_OFFLOAD_UDP_CKSUM |
DEV_TX_OFFLOAD_TCP_CKSUM,

Fixes: a46f8d584eb8 ("net/failsafe: add fail-safe PMD")
Cc: stable@dpdk.org
Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>