HID: apple: remove unused members from struct apple_sc_backlight

The backlight members in struct apple_sc_backlight are unused. They were
added in commit 9018eacbe623 (HID: apple: Add support for keyboard
backlight on certain T2 Macs.), but never used.

As this is not a struct to communicate with the HW, remove these.

Found by https://github.com/jirislaby/clang-struct.

Signed-off-by: Jiri Slaby (SUSE) <[e-mail]>
Cc: Paul Pawlowski <[e-mail]>
Cc: Aun-Ali Zaidi <[e-mail]>
Cc: Aditya Garg <[e-mail]>
Cc: Jiri Kosina <[e-mail]>
Cc: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-apple.c

···
 struct apple_sc_backlight {
 	struct led_classdev cdev;
 	struct hid_device *hdev;
-	unsigned short backlight_off, backlight_on_min, backlight_on_max;
 };
 
 struct apple_sc {