fm10k: fix crash when closing

fm10k: fix crash when closing

When the fm10k port is closed, both func tx_queue_clean() and
fm10k_tx_queue_release_mbufs_vec() will try to release buffer in
SW ring. The latter func won't do sanity check on those pointers
and cause crash.

The fix removed Vector TX buffer release func since it can share
the release functions with regular TX.

Fixes: fb9066e479a6 ("fm10k: reset and release mbuf for vector Tx")

Signed-off-by: Chen Jing D(Mark) <jing.d.chen@intel.com>
Acked-by: Michael Qiu <michael.qiu@intel.com>