net/bnxt: fix memory leak during queue restart

net/bnxt: fix memory leak during queue restart

During port 0 rxq 1 start ie queue start,
bnxt_free_hwrm_rx_ring() we are clearing the pointers to mbuf array.
Due to this we overwrite the queue with fresh mbuf allocations
causing previously allocated mbufs to leak.
Add a check before allocating mbuf to replenish only empty mbuf slots
in the RxQ.

Fixes: 2eb53b134aae ("net/bnxt: add initial Rx code")
Cc: stable@dpdk.org
Signed-off-by: Rahul Gupta <rahul.gupta@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>