asahi: fix get_batch with compute batches

we'll be able to switch between compute and gfx queues soon, handle that instead
of assert failing.

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

src/gallium/drivers/asahi/agx_batch.c

@@ -310,7 +310,7 @@ agx_get_batch_for_framebuffer(struct agx_context *ctx,
 struct agx_batch *
 agx_get_batch(struct agx_context *ctx)
 {
-   if (!ctx->batch) {
+   if (!ctx->batch || agx_batch_is_compute(ctx->batch)) {
       ctx->batch = agx_get_batch_for_framebuffer(ctx, &ctx->framebuffer);
       agx_dirty_all(ctx);
    }