drm/xe/display: Add intel_plane_initial_vblank_wait

We're changing the driver to have no interrupts during early init for
Xe, so we poll the PIPE_FRMSTMSMP counter instead.

Interrupts cannot be enabled during FB readout because memirq's requires
an allocation. This would overwrite the FB we want to read out.

While it might be possible to also run do the same in i915 and run
it without interrupts, the platforms i915 supports had a less clear
distinction between display and graphics. For this reason I choose
only to touch Xe for now.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250121142850.4960-1-dev@lankhorst.se


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