anv: Add and use color auxiliary buffer helpers

anv: Add and use color auxiliary buffer helpers

v2:
- Check for aux levels in layer helper (Jason Ekstrand)
- Don't assert aux is present, return 0 if it isn't.
- Use the helpers.
v3:
- Make the helpers aspect-agnostic (Jason Ekstrand)
- Drop anv_image_has_color_aux()

Signed-off-by: Nanley Chery <nanley.g.chery@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com> (v2)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>