lima: add support for gl_PointSize

GP handles gl_PointSize similar to gl_Position, i.e. it needs
separate buffer and it has special type in varying descriptors, also
for indexed draw we need to emit special PLBU command to pass
address of gl_PointSize buffer.

Blob also clamps gl_PointSize to 1 .. 100 (as well as line width),
so let's do the same.

Reviewed-by: Andreas Baierl <ichgeh@imkreisrum.de>
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>

src/gallium/drivers/lima/lima_program.c

@@ -101,6 +101,7 @@ lima_program_optimize_vs_nir(struct nir_shader *s)
    bool progress;
 
    NIR_PASS_V(s, nir_lower_viewport_transform);
+   NIR_PASS_V(s, nir_lower_point_size, 1.0f, 100.0f);
    NIR_PASS_V(s, nir_lower_io, nir_var_all, type_size, 0);
    NIR_PASS_V(s, nir_lower_load_const_to_scalar);
    NIR_PASS_V(s, lima_nir_lower_uniform_to_scalar);