net/bnxt: fix jumbo frame configuration in firmware

In order to prevent reconfiguration of firmware resources for every
MTU change, configure FW with max MTU value using hwrm_func_cfg
to support all frame sizes. There is no need to overwrite the driver
level MTU variable data->mtu with the FW MTU.

Fixes: 905cd45ce30e ("net/bnxt: use configured MTU during load")
Cc: stable@dpdk.org
Signed-off-by: Rahul Gupta <rahul.gupta@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>