net/mlx5: Decrease default mr cache size

[ Upstream commit e8b26b2135dedc0284490bfeac06dfc4418d0105 ]

Delete initialization of high order entries in mr cache to decrease initial
memory footprint. When required, the administrator can populate the
entries with memory keys via the /sys interface.

This approach is very helpful to significantly reduce the per HW function
memory footprint in virtualization environments such as SRIOV.

Fixes: 9603b61d ("mlx5: Move pci device handling from mlx5_ib to mlx5_core")
Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reported-by: Shalom Toledo <shalomt@mellanox.com>
Acked-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>