zink: store the default variant hash for a program

the first created pipeline with a program is the default variants, and
this is likely to be the most common, so we can store the hash to avoid
needing to recalc it later

Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11740>

src/gallium/drivers/zink/zink_program.c

@@ -447,6 +447,7 @@ zink_create_gfx_program(struct zink_context *ctx,
    assign_io(prog, prog->shaders);
 
    update_shader_modules(ctx, prog->shaders, prog, false);
+   prog->default_variant_hash = ctx->gfx_pipeline_state.module_hash;
 
    for (int i = 0; i < ARRAY_SIZE(prog->pipelines); ++i) {
       prog->pipelines[i] = _mesa_hash_table_create(NULL,

src/gallium/drivers/zink/zink_program.h

@@ -101,6 +101,7 @@ struct zink_gfx_program {
 
    struct zink_shader *shaders[ZINK_SHADER_COUNT];
    struct hash_table *pipelines[11]; // number of draw modes we support
+   uint32_t default_variant_hash;
 };
 
 struct zink_compute_program {