dt-bindings: serial: rsci: Drop "uart-has-rtscts: false"

dt-bindings: serial: rsci: Drop "uart-has-rtscts: false"

Drop "uart-has-rtscts: false" from binding as the IP supports hardware
flow control on all SoCs.

Cc: stable@kernel.org
Fixes: 25422e8f46c1 ("dt-bindings: serial: Add compatible for Renesas RZ/T2H SoC in sci")
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://patch.msgid.link/20251114101350.106699-2-biju.das.jz@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>