net/bnxt: fix ring group free

net/bnxt: fix ring group free

Added an invalid fw_grp_id check inside bnxt_hwrm_ring_grp_free().
This will prevent invalid fw_grp_id to be passed to the FW which can
result in an error.
This fixes the following failure in the "port stop" -> "port start"
sequence:

bnxt_hwrm_ring_grp_free(): error 2:0:00000000:0204
bnxt_hwrm_ring_grp_free(): error 2:0:00000000:0204

Fixes: 9b63c6fd70e3 ("net/bnxt: support Rx/Tx queue start/stop")
Cc: stable@dpdk.org
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Lance Richardson <lance.richardson@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>