tu: Fix buffer overflow optimizing MSRTT.

i is a subpass number, j is the attachment number we're trying to turn
into an attachment.

Fixes: f6c7f16322 ("tu: Implement VK_EXT_multisampled_render_to_single_sampled")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38684>

src/freedreno/vulkan/tu_pass.cc

@@ -649,7 +649,7 @@ tu_render_pass_opt_resolve_unresolve(struct tu_render_pass *pass)
                   */
                  (j == subpass->color_count ?
                  subpass->depth_stencil_attachment.attachment :
-                 subpass->color_attachments[i].attachment) >=
+                 subpass->color_attachments[j].attachment) >=
                 pass->user_attachment_count &&
                 /* Check that it's the last use and the original attachment is
                  * not stored.