drm/i915: Clean up transcoder_to_stream_enc_status()

drm/i915: Clean up transcoder_to_stream_enc_status()

Drop the pointless middle man variable and just return the
correct thing directly.  And while at it change the return
type to u32 since this is a register value we're returning.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220912111814.17466-3-ville.syrjala@linux.intel.com
Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>