net: sfp: remove unused ctype.h include

An include of linux/ctype.h was added in commit 1323061a
("net: phy: sfp: Add HWMON support for module sensors") but nothing
was used from this header file. Remove this unnecessary include.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/sfp.c

 // SPDX-License-Identifier: GPL-2.0
-#include <linux/ctype.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>