glsl: don't expose imageAtomicIncWrap for signed image

The spec says that it's only allowed for unsigned ones.
Same from imageAtomicDecWrap.

Fixes: fc0a2e5d017 ("glsl: add EXT_shader_image_load_store new image functions")
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5688>
1 file changed