drm/i915/display/i9xx: Add a disable_tiling() for i9xx planes

drm/i915/display/i9xx: Add a disable_tiling() for i9xx planes

drm_panic draws in linear framebuffer, so it's easier to re-use the
current framebuffer, and disable tiling in the panic handler, to show
the panic screen.
This assumes that the alignment restriction is always smaller in
linear than in tiled.
It also assumes that the linear framebuffer size is always smaller
than the tiled.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250624091501.257661-4-jfalempe@redhat.com
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>