bnxt_need_reserve_rings() determines if any resources have changed and
requires new reservation with firmware.  The NQ checking is currently
just an approximation.  Improve the NQ checking logic to make it
accurate.  NQ reservation is only needed on 57500 PFs.  This fix will
eliminate unnecessary reservations and will reduce NQ reservations
when some NQs have been released on 57500 PFs.

Fixes: c0b8cda0 ("bnxt_en: Fix NQ/CP rings accounting on the new 57500 chips.")
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>