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: 9c6d778800b9 ("USB: core: Prevent nested device-reset calls")
Cc: <[e-mail]>
Reported-by: Stephen Rothwell <[e-mail]>
Reviewed-by: Bagas Sanjaya <[e-mail]>
Signed-off-by: Alan Stern <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/core/hub.c

···
  *
  * 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.