mlx5 core infrastructure updates and fixes.

From Eran:
 - Add MPEGC (Management PCIe General Configuration) registers and btis
 - Fix tristate and description for MLX5 module

rom Feras:
 - Add hardware structures for the firmware tracer

From Jainbo:
 - Core support for double vlan push/pop steering action

From Max:
 - Add XRQ commands definitions

From Noa:
 - Add missing SET_DRIVER_VERSION command translation

From Roi:
 - Use ERR_CAST() instead of coding it

From Tariq:
 - Better return types for CQE API

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>