USB: HWA: constify hc_driver structures

The hc_driver structure is only passed as the first argument to
usb_create_hcd, which is declared as const.  Thus the hc_driver structure
itself can be const.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>