ac/surface: only adjust pitch if surf_pitch was modified

ac/surface: only adjust pitch if surf_pitch was modified

Modifying pitch for all LINEAR surface isn't correct;
the original change that modified surf_pitch was only
intended for YUV textures.

This fixes vkGetImageSubresourceLayout rowPitch return value
for VK_FORMAT_BC3_UNORM_BLOCK + VK_IMAGE_TILING_LINEAR.

Fixes: fcc499d5 (ac/surface: adjust gfx9.pitch[*] based on surf->blk_w)

v2: add check for UYVY format (Pierre-Eric)
v3: move blk_w division to above if check (Pierre-Eric)

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21595>