turnip, freedreno: Always write GRAS_LRZ_MRT_BUF_INFO_0

This fixes flakes in dEQP-VK.pipeline.stencil.nocolor.format.* when run after ycbcr tests. Apparently LRZ needs to know if there's a media format enabled even if there are no color attachments, so we need to write something here. Presumably any "normal" format would work but 0 seems like a good neutral choice.

Fixes: 9c895e13 ("tu: Emit GRAS_LRZ_MRT_BUF_INFO_0")