if_bnxt: Added support for mgmt interface for passthrough hwrms

if_bnxt: Added support for mgmt interface for passthrough hwrms

Added support for application management interface. There are two types of commands supported:

1. Firmware IOCTLs: These ioctls are meant for firmware
   consumption. Driver acts as a transport for these.
2. Driver only IOCTLs: These ioctls are meant for driver
   consumption. Driver will serve these ioctls without sending them down
   to firmware.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D36448

(cherry picked from commit 58d84ef87094691bf1ad9608964ec85f120cd34a)