IB/mlx5: Limit mkey page size to 2GB

The maximum page size in the mkey context is 2GB.

Until today, we didn't enforce this requirement in the code,
and therefore, if we got a page size larger than 2GB, we
have passed zeros in the log_page_shift instead of the actual value
and the registration failed.

This patch limits the driver to use compound pages of 2GB for mkeys.

Fixes: e126ba97 ('mlx5: Add driver for Mellanox Connect-IB adapters')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>