drm/i915/frontbuffer: HW tracking for cursor moves to fix PSR lags.

DRM_IOCTL_MODE_CURSOR results in frontbuffer flush before the cursor
plane MMIOs are written to. But this flush should not be necessary for
PSR as hardware tracking triggers PSR exit when MMIOs are written. As
for FBC, the spec says "Flips or changes to plane size and panning" cause
FBC to be nuked. Use origin == ORIGIN_FLIP so that features can ignore
cursor updates in their frontbuffer_flush implementations.

 /sys/kernel/debug/dri/0/i915_fbc_status shows
"Compressing: yes" when I move the cursor around.

v3: Use ORIGIN_FLIP now that pin_to_display does not flush frontbuffer.
v2: Update comment in i915_gem_object_pin_to_display_plane. (Chris)

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180307033420.3086-2-dhinakaran.pandiyan@intel.com