llvmpipe: fix linear fs analysis with nonzero fs outputs

linear fs only works with output 0

cc: mesa-stable

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22135>

src/gallium/drivers/llvmpipe/lp_state_fs_analysis.c

@@ -523,6 +523,8 @@ llvmpipe_fs_analyse_nir(struct lp_fragment_shader *shader)
 {
    if (shader->info.base.num_inputs <= LP_MAX_LINEAR_INPUTS &&
        shader->info.base.num_outputs == 1 &&
+       shader->info.base.output_semantic_name[0] == TGSI_SEMANTIC_COLOR &&
+       shader->info.base.output_semantic_index[0] == 0 &&
        !shader->info.indirect_textures &&
        !shader->info.sampler_texture_units_different &&
        shader->info.num_texs <= LP_MAX_LINEAR_TEXTURES &&