drm/i915/psr: Set plane id bit in crtc_state->async_flip_planes for PSR

drm/i915/psr: Set plane id bit in crtc_state->async_flip_planes for PSR

Currently plane id bit is set in crtc_state->async_flip_planes only when
async flip toggle workaround is needed. We want to utilize
crtc_state->async_flip_planes further in Selective Fetch calculation.

v2:
  - rework if-else if to if-if
  - added comment updated

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20251204070718.1090778-2-jouni.hogander@intel.com