USB: misc: iowarrior: remove redundant assignment to variable io_res

The variable io_res is being assigned a value that is never read, it is
either being re-assigned a new value that is read later or it's not used
depending on the cases in the following switch statement. The assignment
is redundant and can be removed. Cleans up clang scan build warning:

drivers/usb/misc/iowarrior.c:504:2: warning: Value stored to 'io_res'
is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/misc/iowarrior.c

···
 		dev->minor, cmd, arg);
 
 	retval = 0;
-	io_res = 0;
 	switch (cmd) {
 	case IOW_WRITE:
 		if (dev->product_id == USB_DEVICE_ID_CODEMERCS_IOW24 ||