drm/i915/psr: Add psr sink error status into sink status debugfs

Normally PSR errors detected by the panel are triggering HPD interrupt and
seen as error in dmesg. Some panels are not triggering the interrupt even
it is requested and they are detecting error. Due to this it would be good
to have possibility to check panel detected errors. Add PSR error status
into PSR sink status debugfs interface.

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230828083107.1520501-1-jouni.hogander@intel.com