net/ice: fix unchecked Tx cleanup error

net/ice: fix unchecked Tx cleanup error

Coverity complains of unchecked return value warning of
ice_xmit_cleanup, while this cleanup is opportunistic and will not cause
problems if it fails. So instead of checking the return value of
ice_xmit_cleanup and return in case of cleanup failure, we directly cast
it to void function to make the Coverity happy.

Coverity issue: 353623
Fixes: 17c7d0f9d6a4 ("net/ice: support basic Rx/Tx")
Cc: stable@dpdk.org
Signed-off-by: Sunil Pai G <sunil.pai.g@intel.com>
Acked-by: Xiaolong Ye <xiaolong.ye@intel.com>