v3dv: fix sampling from stencil aspect of a combined depth/stencil image

When sampling the stencil aspect we want to reinterpret the D24S8 format
as RGBA8 and read stencil values from the R component.

Fixes:
dEQP-VK.renderpass.suballocation.formats.d24_unorm_s8_uint.input.*

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