USB: OHCI: don't look at the root hub to get the number of ports

This patch (as1371) fixes a small bug in ohci-hcd.  The HCD already
knows how many ports the controller has; there's no need to go looking
at the root hub's usb_device structure to find out.  Especially since
the root hub's maxchild value is set correctly only while the root hub
is bound to the hub driver.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>