ir_to_mesa: Use uniform_field_visitor to add all struct fields to parameter list

ir_to_mesa: Use uniform_field_visitor to add all struct fields to parameter list

Previously the uniform was passed as single, whole structure to
_mesa_add_parameter.  This was completely bogus and resulted in a
DataType of 0 (instead of a valid GLSL type enum).

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41980
Tested-by: Brian Paul <brianp@vmware.com>
Cc: Bryan Cain <bryancain3@gmail.com>
Cc: Vinson Lee <vlee@vmware.com>
Cc: José Fonseca <jfonseca@vmware.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>