drm/i915: Add intel_bo_panic_setup() and intel_bo_panic_finish()

Implement both functions for i915 and xe, they prepare the work for
drm_panic support.
They both use kmap_try_from_panic(), and map one page at a time, to
write the panic screen on the framebuffer.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250624091501.257661-8-jfalempe@redhat.com


Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>