zink: reorder create_stream_output_target to fix failure case leak

the previous version of this leaked a reference to the streamout buffer here

thanks to deltragon on my blog for pointing this out!

Fixes: 37778fcd9a ("zink: implement transform feedback support to finish off opengl 3.0")

Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6457>

src/gallium/drivers/zink/zink_context.c

@@ -1002,12 +1002,6 @@ zink_create_stream_output_target(struct pipe_context *pctx,
    if (!t)
       return NULL;
 
-   t->base.reference.count = 1;
-   t->base.context = pctx;
-   pipe_resource_reference(&t->base.buffer, pres);
-   t->base.buffer_offset = buffer_offset;
-   t->base.buffer_size = buffer_size;
-
    /* using PIPE_BIND_CUSTOM here lets us create a custom pipe buffer resource,
     * which allows us to differentiate and use VK_BUFFER_USAGE_TRANSFORM_FEEDBACK_COUNTER_BUFFER_BIT_EXT
     * as we must for this case
@@ -1018,6 +1012,12 @@ zink_create_stream_output_target(struct pipe_context *pctx,
       return NULL;
    }
 
+   t->base.reference.count = 1;
+   t->base.context = pctx;
+   pipe_resource_reference(&t->base.buffer, pres);
+   t->base.buffer_offset = buffer_offset;
+   t->base.buffer_size = buffer_size;
+
    return &t->base;
 }