bnxt_en: Fix VNIC accounting when enabling aRFS on 57500 chips.

Unlike legacy chips, 57500 chips don't need additional VNIC resources
for aRFS/ntuple.  Fix the code accordingly so that we don't reserve
and allocate additional VNICs on 57500 chips.  Without this patch,
the driver is failing to initialize when it tries to allocate extra
VNICs.

Fixes: ac33906c

 ("bnxt_en: Add support for aRFS on 57500 chips.")
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>