dt-bindings: serial: renesas,scif: Remove redundant renesas,scif-r9a07g054

This patch removes redundant "renesas,scif-r9a07g054" from binding
documentation as it uses renesas,scif-r9a07g044 fallback.

Whilst remove the additional renesas,scif-r9a07g054 from Items.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20220207142213.19552-1-biju.das.jz@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>