mlxsw: pci: Introduce helpers to work with multiple CQE versions

Introduce definitions of fields in CQE version 1 and 2. Also, introduce
common helpers that would call appropriate version-specific helpers
according to the version enum passed.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>