RDMA/mlx5: Delete get_num_static_uars function

There is no need to keep get_num_static_uars in the headers file
as it is not shared and used only once.

Link: https://lore.kernel.org/r/11d78568c3c6ba588ee8465e0d10d96145fc825c.1642960830.git.leonro@nvidia.com


Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>