turnip: disable UBWC for SNORM formats
I have a test case that copies a VK_FORMAT_R8G8B8A8_UNORM image to a VK_FORMAT_R8G8B8A8_SNORM image and then samples from the destination image. There are corruptions when the destination image is UBWC-compressed. I tried forcing staging blit in tu_copy_image_to_image but that did not help.
The gallium driver disables UBWC for SNORM formats (and many more) in ok_ubwc_format. Let's follow it.
Closes: #6480 (closed)