intel/batch_decoder: Don't clame vec4 vs/gs/tcs shaders on Gen11+

Because we hard-coded the default to vec4, any platform where it doesn't
have a "Dispatch Mode" field gets vec4 by default.  This includes Gen11+
where vec4 is no longer a thing.  Change the default so it works on
newer hardware.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7084>

src/intel/common/gen_batch_decoder.c

@@ -507,7 +507,7 @@ decode_single_ksp(struct gen_batch_decode_ctx *ctx, const uint32_t *p)
    struct gen_group *inst = gen_ctx_find_instruction(ctx, p);
 
    uint64_t ksp = 0;
-   bool is_simd8 = false; /* vertex shaders on Gen8+ only */
+   bool is_simd8 = ctx->devinfo.gen >= 11; /* vertex shaders on Gen8+ only */
    bool is_enabled = true;
 
    struct gen_field_iterator iter;