v3dv: fix incorrect attachment reference

We were using the subpass render target index to index into the framebuffer,
which is not correct, since the framebuffer is defined for the render pass.
We should use the attachment index instead.

Fixes:
dEQP-VK.renderpass.suballocation.attachment_allocation.roll.{40,48}

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6766>
1 file changed