panvk: Non-destructively stub GetRenderAreaGranularity

Don't crash.  Just print a warning and return 1x1.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15285>

src/panfrost/vulkan/panvk_pass.c

@@ -218,5 +218,6 @@ panvk_GetRenderAreaGranularity(VkDevice _device,
                                VkRenderPass renderPass,
                                VkExtent2D *pGranularity)
 {
-   panvk_stub();
+   /* TODO: Return the actual tile size for the render pass? */
+   *pGranularity = (VkExtent2D) { 1, 1 };
 }