USB: core: Fix RST error in hub.c

A recent commit added an invalid RST expression to a kerneldoc comment
in hub.c.  The fix is trivial.

Fixes: 9c6d778800 ("USB: core: Prevent nested device-reset calls")
Cc: <stable@vger.kernel.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/YxDDcsLtRZ7c20pq@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hub.c

@@ -6039,7 +6039,7 @@ re_enumerate:
  *
  * Return: The same as for usb_reset_and_verify_device().
  * However, if a reset is already in progress (for instance, if a
- * driver doesn't have pre_ or post_reset() callbacks, and while
+ * driver doesn't have pre_reset() or post_reset() callbacks, and while
  * being unbound or re-bound during the ongoing reset its disconnect()
  * or probe() routine tries to perform a second, nested reset), the
  * routine returns -EINPROGRESS.