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.comReviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>