Support short HWRM commands

New Stratus bnxt devices require support for short HWRM commands for VFs
to function. Enable their use, but only use them if it's both supported
and required... prefer the long HWRM commands when possible.

Submitted by: Bhargava Chenna Marreddy <bhargava.marreddy@broadcom.com>
Sponsored by: Broadcom Limited
Differential Revision: https://reviews.freebsd.org/D13269?id=36180