bnxt_en: Allocate TQM ring context memory according to fw specification.

Newer firmware spec. will specify the number of TQM rings to allocate
context memory for.  Use the firmware specified value and fall back
to the old value derived from bp->max_q if it is not available.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>