drm/i915/overlay: Don't use fetch_and_zero() in display code

drm/i915/overlay: Don't use fetch_and_zero() in display code

We don't generally want fetch_and_zero() on the display side, so
stop using it in the display side intel_overlay_cleanup().
Fortunately we don't really have anything to do here apart from
freeing the data. And we'll keep on clearing the pointer, just
in case something somewhere cares about it.

Note that once i915_overlay_cleanup() is converted to the parent
interface we can't call it unconditionally (as xe won't have it).
So we need to keep the early bailout for overlay==NULL.

v2: Adjust the commit message since we do apparently
    have fetch_and_zero() in display code as well (Jani)
v3: Skip i915_overlay_cleanup() if the overlay wasn't initialized

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260226130113.16714-1-ville.syrjala@linux.intel.com