IB/usnic: usnic should not select INFINIBAND_USER_ACCESS

This driver doesn't provide any kernel services, it only provides
an interface via uverbs, so it should depend on, not select, uverbs
support.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>