i915 yet don't support PSR in Apple panels, so lets keep it disabled
while we work on that.

v2: Renamed DP_DPCD_QUIRK_PSR_NOT_CURRENTLY_SUPPORTED to
DP_DPCD_QUIRK_NO_PSR (Ville)

v3:
Adding documentation to DP_DPCD_QUIRK_NO_PSR(Dhinakaran and Jani)
Fixed typo in comment of the new quirk entry(Jani)

Fixes: 598c6cfe (drm/i915/psr: Enable PSR1 on gen-9+ HW)
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181204003403.23361-1-jose.souza@intel.com
(cherry picked from commit 7c5c641a)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>