drm/i915: Ditch intel_edp_psr_update

We have _enable/_disable interfaces now for the modeset sequence and
intel_edp_psr_exit for workarounds.

The callsites in intel_display.c are all redundant with the modeset
sequence enable/disable calls in intel_ddi.c. The one in
intel_sprite.c is real and needs to be switched to psr_exit.

If this breaks anything then we need to augment the enable/disable
functions accordingly.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>