USB: core: Fix RST error in hub.c

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: 20cc75abd00d ("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>