iris: clamp PointWidth in 3DSTATE_SF like i965 does
Values match how MinimumPointWidth, MaximumPointWidth is setup. This fixes assert hit in debug build when packing the struct with too large value for genxml. Signed-off-by:Tapani Pälli <tapani.palli@intel.com> Reviewed-by:
Lionel Landwerlin <lionel.g.landwerlin@intel.com> Cc: mesa-stable Part-of: <mesa/mesa!9942> (cherry picked from commit b2af4193)