IB/mlx5: fix VFs callback function prototypes

The previous patch that added a couple of callback functions put
the declarations inside of an #ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING,
which causes the build to fail if that option is disabled:

drivers/infiniband/hw/mlx5/main.c: In function 'mlx5_ib_add':
drivers/infiniband/hw/mlx5/main.c:2358:31: error: 'mlx5_ib_get_vf_config' undeclared (first use in this function)

This moves the four declarations below the #ifdef section so they
are always available.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: eff901d3

 ("IB/mlx5: Implement callbacks for manipulating VFs")
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>