bnxt_en: Setup default RSS map in all scenarios.

The recent changes to support user-defined RSS map assume that RX
rings are always reserved and the default RSS map is set after the
RX rings are successfully reserved.  If the firmware spec is older
than 1.6.1, no ring reservations are required and the default RSS
map is not setup at all.  In another scenario where the fw Resource
Manager is older, RX rings are not reserved and we also end up with
no valid RSS map.

Fix both issues in bnxt_need_reserve_rings().  In both scenarios
described above, we don't need to reserve RX rings so we need to
call this new function bnxt_check_rss_map_no_rmgr() to setup the
default RSS map when needed.

Without valid RSS map, the NIC won't receive packets properly.

Fixes: 1667cbf6 ("bnxt_en: Add logical RSS indirection table structure.")
Reviewed-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>