net/bnxt: support tunneling

net/bnxt: support tunneling

Add support for udp_tunnel_port_add/del dev_ops to configure a UDP port
for VXLAN and Geneve Tunnel protocols.

The HWRM supports only one global destination port for a tunnel type,
use a reference counter to keep track of its usage.
Cache the configured VXLAN/Geneve ports and use that value to check
if the right UDP port is being freed up.
Skip calling bnxt_hwrm_tunnel_dst_port_alloc if the same UDP port is
being programmed.
Skip calling bnxt_hwrm_tunnel_dst_port_free if no UDP port has been
configured.

Also update tx offload capabilities

Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>