cxgb4: Report tid start range correctly for T6

For T6, tid start range should be read from
LE_DB_ACTIVE_TABLE_START_INDEX_A register.

Signed-off-by: Arjun Vynipadath <arjun@chelsio.com>
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>