sh-pfc: r8a7790: Remove trailing '_TANS' string from RTS/CTS pins

The RTS/CTS pins have been renamed in the datasheet, rename them here as
well.

Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>