IB/hfi1 Use correct type for num_user_context

The module parameter num_user_context is defined as 'int' and
defaults to -1.  The module_param_named() says that it is uint.

Correct module_param_named() type information and update the modinfo
text to reflect the default value.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>