drm/i915: Start tracking PSR state in crtc state

drm/i915: Start tracking PSR state in crtc state

Add the minimal amount of PSR tracking into the crtc state. This allows
precomputing the possibility of using PSR correctly, and it means we can
safely call the psr enable/disable functions for any DP endcoder.

As a nice bonus we get rid of some more crtc->config usage, which we
want to kill off eventually.

v2: Fix 'goto unlock' fail in intel_psr_enable() (Jani)
    Check intel_dp_is_edp() in is_edp_psr() (Jani)

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171012130201.21318-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>