scripts/spelling.txt: add "swith" pattern and fix typo instances

Fix typos and add the following to the scripts/spelling.txt:

  swith||switch
  swithable||switchable
  swithed||switched
  swithing||switching

While we are here, fix the "update" to "updates" in the touched hunk in
drivers/net/wireless/marvell/mwifiex/wmm.c.

Link: http://lkml.kernel.org/r/1481573103-11329-2-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/net/usb/kalmia.c

@@ -343,7 +343,7 @@ static const struct driver_info kalmia_info = {
 static const struct usb_device_id products[] = {
 	/* The unswitched USB ID, to get the module auto loaded: */
 	{ USB_DEVICE(0x04e8, 0x689a) },
-	/* The stick swithed into modem (by e.g. usb_modeswitch): */
+	/* The stick switched into modem (by e.g. usb_modeswitch): */
 	{ USB_DEVICE(0x04e8, 0x6889),
 		.driver_info = (unsigned long) &kalmia_info, },
 	{ /* EMPTY == end of list */} };