bnxt_en: L2-RoCE driver communication interface

• Added Aux bus support for RoCE.
• Implemented the ulp ops that are required by RoCE driver.
• Restructure context memory data structures
• DBR pacing support

Reviewed by: imp
Approved by: imp
Differential revision: https://reviews.freebsd.org/D45006

(cherry picked from commit 050d28e13cdede7528944c0abf8d0455729c63fd)