cxgb4vf: Move fl_starv_thres into adapter->sge data structure

Move fl_starv_thres into adapter->sge data structure since it
_could_ be different from adapter to adapter.  Also move other per-adapter
SGE values which had been treated as driver globals into adapter->sge.

Based on original work by Casey Leedom <leedom@chelsio.com>

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>