IB/mlx5: Limit query HCA clock

When PAGE_SIZE is larger than 4K, the user shouldn't be able to query
the HCA core clock. This counter is within 4KB boundary and the
user-space shall not read information that's after this boundary.

Fixes: b368d7cb

 ('IB/mlx5: Add hca_core_clock_offset to...')
Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Noa Osherovich <noaos@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>