drm/i915/adlp: Extend PSR2 support in transcoder B

PSR2 is supported in transcoder A and B on Alderlake-P.

v2:
- explicity checking for transcoder A and B to avoid invalid transcoder

BSpec: 49185
Reviewed-by: Jouni Högander <jouni.hogander@intel.com> # v1
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Jouni Hogander <jouni.hogander@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com> # v2
Link: https://patchwork.freedesktop.org/patch/msgid/20211027180545.55660-1-jose.souza@intel.com