drm/xe/display: Separate the d3cold and non-d3cold runtime PM handling

For clarity separate the d3cold and non-d3cold runtime PM handling. The
only change in behavior is disabling polling later during runtime
resume. This shouldn't make a difference, since the poll disabling is
handled from a work, which could run at any point wrt. the runtime
resume handler. The work will also require a runtime PM reference,
syncing it with the resume handler.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241009194358.1321200-4-imre.deak@intel.com