usb: gadget: configfs: Ignore trailing LF for user strings to cdev

Since commit c033563220e0f7a8
("usb: gadget: configfs: Attach arbitrary strings to cdev")
a user can provide extra string descriptors to a USB gadget via configfs.

For "manufacturer", "product", "serialnumber", setting the string via
configfs ignores a trailing LF.

For the arbitrary strings the LF was not ignored.

This patch ignores a trailing LF to make this consistent with the existing
behavior for "manufacturer", ... string descriptors.

Fixes: c033563220e0 ("usb: gadget: configfs: Attach arbitrary strings to cdev")
Cc: stable <[e-mail]>
Signed-off-by: Ingo Rohloff <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/gadget/configfs.c

···
 {
 	struct gadget_string *string = to_gadget_string(item);
 	int size = min(sizeof(string->string), len + 1);
+	ssize_t cpy_len;
 
 	if (len > USB_MAX_STRING_LEN)
 		return -EINVAL;
 
-	return strscpy(string->string, page, size);
+	cpy_len = strscpy(string->string, page, size);
+	if (cpy_len > 0 && string->string[cpy_len - 1] == '\n')
+		string->string[cpy_len - 1] = 0;
+	return len;
 }
 CONFIGFS_ATTR(gadget_string_, s);