bnxt_re/libbnxtre: Add RoCE support for BCM576xx controllers
Added RoCE support for BCM576xx controllers with below changes,
- Update the BAR offsets for handling BCM576xx controllers.
Use the values populated by the L2 driver for getting the
Doorbell offsets.
- Use msn index instead of tail to pull psn table entry.
- Temporarily disable dbr pacing feature untill it is
fully implemented.
- Add support for 400G speed.
Reviewed by: ssaxena
Differential Revision: https://reviews.freebsd.org/D54521
MFC after: 3 days
(cherry picked from commit 92ba9b2fe58910b1d2cd6cd34b5ec093f0d9f700)