net/cxgbe: support Source MAC Table

net/cxgbe: support Source MAC Table

Source MAC Table (SMT) is used for storing Source MAC
addresses to be written in packets transmitted on the
wire. Hence, the SMT table can be used for overwriting
Source MAC addresses in packets, hitting corresponding
filter rules inserted by the rte_flow API.

Query firmware for SMT start and size information available
to the underlying PF. Allocate and maintain the corresponding
driver's copy of the hardware SMT table, with appropriate
refcount mechanism. If SMT information is not available, then
use the entire hardware SMT table.

Signed-off-by: Karra Satwik <kaara.satwik@chelsio.com>
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>