RDMA/uverbs: Fix incorrect variable type

RDMA/uverbs: Fix incorrect variable type

Fix incorrect type of max_entries in UVERBS_METHOD_QUERY_GID_TABLE -
max_entries is of type size_t although it can take negative values.

The following static check revealed it:

drivers/infiniband/core/uverbs_std_types_device.c:338 ib_uverbs_handler_UVERBS_METHOD_QUERY_GID_TABLE() warn: 'max_entries' unsigned <= 0

Fixes: 9f85cbe50aa0 ("RDMA/uverbs: Expose the new GID query API to user space")
Link: https://lore.kernel.org/r/20201208073545.9723-4-leon@kernel.org
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>