staging: comedi: drivers: Fix spelling mistake "nubmer" -> "number"

There is a spelling mistake in a comment. Fix it.
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20210407111301.486853-1-colin.king@canonical.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/addi_apci_16xx.c

@@ -110,7 +110,7 @@ static int apci16xx_auto_attach(struct comedi_device *dev,
 	dev->iobase = pci_resource_start(pcidev, 0);
 
 	/*
-	 * Work out the nubmer of subdevices needed to support all the
+	 * Work out the number of subdevices needed to support all the
 	 * digital i/o channels on the board. Each subdevice supports
 	 * up to 32 channels.
 	 */