drm/i915/psr: Add Early Transport status boolean into intel_psr

drm/i915/psr: Add Early Transport status boolean into intel_psr

Currently we are purely relying on psr2_su_region_et_valid. Add new boolean
value into intel_psr struct indicating whether Early Transport is enabled
or not and use it instead of psr2_su_region_et_valid for getting Early
Transport status information.

Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240529093849.1016172-2-jouni.hogander@intel.com