net/mlx5: Add pci AtomicOps request

Calling pci_enable_atomic_ops_to_root enables AtomicOp requests to pci
root port.

AtomicOp requests will be enabled only if the completer and all
intermediate pci bridges support PCI atomic operations.
This, together with appropriate settings in the NVCONFIG should enable
PCI atomic operations on the device.

PCI atomic operations were first introduced in PCI Express Base Specification
2.1. The Supported operations are Swap (Unconditional Swap), CAS (Compare and
Swap) and FetchAdd (Fetch and Add).

Unlike other atomic operation modes PCI atomic operations gives the user
the option to do atomic operations on local memory, without involving verbs
api, without it compromising the operation's atomicity.

Signed-off-by: Michael Guralnik <michaelgur@mellanox.com>
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>