IB/core: Replace setting the zero values in ib_uverbs_ex_query_device

The setting to zero during variable initialization eliminates
the need to explicitly set to zero variables and structures.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>