USB: don't build PCI quirks if USB support isn't configured

The USB PCI quirks code gets built into the kernel whenever CONFIG_PCI
is enabled, even if CONFIG_USB is not set.  This can cause unnecessary
messages to show up in the kernel log, such as "CONFIG_USB_XHCI_HCD is
turned off, defaulting to EHCI" (which makes no sense when the kernel
has been configured without host-side USB support).

This patch addresses the problem by building pci-quirks.o only when
CONFIG_PCI and CONFIG_USB are both enabled.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>