v3dv: Loosen an assert in copy_buffer_to_image_shader

In 99ac7f2de198 ("v3dv: Don't use color aspects for depth/stencil images"), we stopped using color aspects for depth/stencil images in a bunch of cases. This causes us to trigger an assert in copy_buffer_to_image_shader where it assumes 16-bit is always color but now it can also be D16_UNORM. The assert isn't protecting us from anything we weren't already doing before so we can just loosen it a bit.

Fixes: 99ac7f2de198 ("v3dv: Don't use color aspects for depth/stencil images")