glsl: set vector_elements to 1 for samplers

glsl: set vector_elements to 1 for samplers

I don't see any reasons why vector_elements is 1 for images and
0 for samplers. This increases consistency and allows to clean
up some code a bit.

This will also help for ARB_bindless_texture.

No piglit regressions with RadeonSI.

This time the Intel CI system doesn't report any failures.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>