mlxsw: pci: Rename header with HW definitions

pci.h needs to be used for inner function declarations. So move the
original one to more appropriate name, pci_hw.h.

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