bnxt_en: Improve resource accounting for SRIOV.

bnxt_en: Improve resource accounting for SRIOV.

When VFs are created, the current code subtracts the maximum VF
resources from the PF's pool.  This under-estimates the resources
remaining in the PF pool.  Instead, we should subtract the minimum
VF resources.  The VF minimum resources are guaranteed to the VFs
and only these should be subtracted from the PF's pool.

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