serial: sh-sci: Remove unused STEPFN() macro

The last user of the STEPFN() macro was removed in commit
d5cb1319 ("serial: sh-sci: Remove manual break debouncing").
Reviewed-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/970387d104dea5bb7ea674bb89229641467e629b.1623076891.git.geert+renesas@glider.beSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sh-sci.c

@@ -841,9 +841,6 @@ static void sci_transmit_chars(struct uart_port *port)
 
 }
 
-/* On SH3, SCIF may read end-of-break as a space->mark char */
-#define STEPFN(c)  ({int __c = (c); (((__c-1)|(__c)) == -1); })
-
 static void sci_receive_chars(struct uart_port *port)
 {
 	struct tty_port *tport = &port->state->port;