glsl: make component_slots() returns 1 for sampler types

glsl: make component_slots() returns 1 for sampler types

It looks inconsistent to return 1 for image types and 0 for
sampler types. Especially because component_slots() is mostly
used by values_for_type() which always returns 1 for samplers.

For bindless, this value will be bumped to 2 because the
ARB_bindless_texture states that bindless samplers/images
should consume two components.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>