Image offsets are compared with the `min_texel_gather_offset` device property as u64 instead of i32.

[LukeP0WERS]

When I updated to the vulkano master branch I got this error:
create_info.stage.entry_point: an `OpImageSample*` or `OpImageFetch*` instruction is performed, but its `ConstOffset` image operand contains a value that is less than the `min_texel_offset` device limit
even though the min_texel_gather_offset for my device is -8 and all of my offsets are 0 or 1.

It should be comparing with i32 instead of u64 here:

vulkano/vulkano/src/pipeline/shader/validate_runtime.rs

Line 2540 in 93b6e94

if offset < properties.min_texel_offset as u64 {

[Rua]

A nice example of how evil as can be!