drm/i915: DDI: call intel_psr_ and _edp_drrs_enable() on pipe updates (v2)

Call intel_psr_enable() and intel_edp_drrs_enable() on pipe updates to make
sure that we enable PSR / DRRS (when applicable) on fastsets.

Note calling these functions when PSR / DRRS has already been enabled is a
no-op, so it is safe to do this on every encoder->update_pipe callback.

Changes in v2:
-Merge the patches adding the intel_psr_enable() and intel_edp_drrs_enable()
 calls into a single patch

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181220132120.15318-3-hdegoede@redhat.com