drm/i915/psr: Add some documentation of variables used in psr code

We are adding more boolean variable into intel_psr and intel_crtc_state
structs. Add some documentation about these for sake of clarity.

v2: Modify has_psr +  has_panel_replay to mean panel replay

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240405113602.992714-2-jouni.hogander@intel.com