USB: fix Kconfig logic for USB_UHCI_HCD

The Kconfig settings for uhci-hcd are too permissive; they allow the
driver to be built without any bus-glue modules configured
(USB_UHCI_HCD enabled, PCI disabled, SPARC_LEON disabled, ARCH_VT8500
enabled, and USB_UHCI_PLATFORM disabled).

This patch fixes the problem by rearranging the dependencies.  Now the
platform-dependent config options don't depend on USB_UHCI_HCD;
instead it depends on them.  Furthermore, there is no user-selectable
choice as to which glue modules will be built.  If USB_UHCI_HCD is
enabled then all applicable bus glues will be built.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>