drm: Remove legacy cursor hotspot code

Atomic modesetting supports mouse cursor offsets via the hotspot
properties that are created on cursor planes. All drivers which
support hotspots are atomic and the legacy code has been implemented
in terms of the atomic properties as well.

Due to the above the lagacy cursor hotspot code is no longer used or
needed and can be removed.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231023074613.41327-8-aesteve@redhat.com