RDMA/mlx5: Reorder calls to pcie_relaxed_ordering_enabled()

RDMA/mlx5: Reorder calls to pcie_relaxed_ordering_enabled()

The mkc is the key for the mkey cache, hence, created in each attempt to
get a cache mkey, while pcie_relaxed_ordering_enabled() is called during
the setting of the mkc, but used only for cases where
IB_ACCESS_RELAXED_ORDERING is set.

pcie_relaxed_ordering_enabled() is an expensive call (26 us). Reorder the
code so the driver will call it only when it is needed.

Link: https://lore.kernel.org/r/684be1366cb1d4f05aa3e78986205e4bc410443a.1644947594.git.leonro@nvidia.com
Signed-off-by: Aharon Landau <aharonl@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>