asahi: rm pointless multisample key bit

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26963>

src/gallium/drivers/asahi/agx_state.c

@@ -2321,7 +2321,6 @@ agx_update_fs(struct agx_batch *batch)
       .clip_plane_enable = ctx->rast->base.clip_plane_enable,
       .nr_samples = nr_samples,
       .layered = util_framebuffer_get_num_layers(&batch->key) > 1,
-      .multisample = msaa,
 
       /* Only lower sample mask if at least one sample is masked out */
       .api_sample_mask =
@@ -2340,7 +2339,7 @@ agx_update_fs(struct agx_batch *batch)
    memcpy(&key.blend, ctx->blend, sizeof(key.blend));
 
    /* Normalize key */
-   if (!key.multisample)
+   if (!msaa)
       key.blend.alpha_to_coverage = false;
 
    return agx_update_shader(ctx, &ctx->fs, PIPE_SHADER_FRAGMENT,

src/gallium/drivers/asahi/agx_state.h

@@ -393,7 +393,6 @@ struct asahi_fs_shader_key {
    uint8_t cull_distance_size;
    uint8_t clip_plane_enable;
    uint8_t nr_samples;
-   bool multisample;
    bool layered;
    enum pipe_format rt_formats[PIPE_MAX_COLOR_BUFS];
 };