RDMA: Remove redundant memset() from query_device callbacks

The core always hands the driver's query_device() callback a zeroed
ib_device_attr. There are only two callers of the op and both clear the
structure before invoking it: setup_device() memsets &device->attrs, and
ib_uverbs_ex_query_device() passes an on-stack structure initialized to {}.

The open-coded memset(props, 0, sizeof(*props)) at the top of the driver
callbacks is therefore redundant. Remove it from all drivers.

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