serial: sh-sci: Drop support for "sci_ick" clock

Since commit 1b463bd5 ("ARM: dts: r8a7794: Rename the serial
port clock to fck") in v4.6, all upstream DTS files call the SCIF
functional clock "fck".

Hence the time is ripe to drop backward-compatibility with old DTBs that
use the old "sci_ick" name.
Reviewed-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/b4103e44d6ac46b6c1c264e2aeac80b39941fe74.1639663832.git.geert+renesas@glider.beSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sh-sci.c

@@ -2784,17 +2784,6 @@ static int sci_init_clocks(struct sci_port *sci_port, struct device *dev)
 			return -EPROBE_DEFER;
 
 		if (IS_ERR(clk) && i == SCI_FCK) {
-			/*
-			 * "fck" used to be called "sci_ick", and we need to
-			 * maintain DT backward compatibility.
-			 */
-			clk = devm_clk_get(dev, "sci_ick");
-			if (PTR_ERR(clk) == -EPROBE_DEFER)
-				return -EPROBE_DEFER;
-
-			if (!IS_ERR(clk))
-				goto found;
-
 			/*
 			 * Not all SH platforms declare a clock lookup entry
 			 * for SCI devices, in which case we need to get the