radeon / r200: Don't pass unused parameters to radeon_viewport

radeon / r200: Don't pass unused parameters to radeon_viewport

The x, y, width, and height parameters aren't used by radeon_viewport,
so don't pass them.  This should make future changes to the
dd_function_table::Viewport interface a little easier.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Jordan Justen <jljusten@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Courtney Goeltzenleuchter <courtney@lunarg.com>