drm/i915: kill ring->get_active_head

All functions are extremely similar, so fold them into one generic
implementation.

This function isn't used anyway, because there's not yet a bsd ring
error state dumper.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
2 files changed