USB: EHCI: miscellaneous cleanups for the library conversion

This patch (as1630) cleans up a few minor items resulting from the
split-up of the ehci-hcd driver:

	Remove the product_desc string from the ehci_driver_overrides
	structure.  All drivers will use the generic "EHCI Host
	Controller" string.  (This was requested by Felipe Balbi.)

	Allow drivers to pass a NULL pointer to ehci_init_driver()
	if they don't have to override any settings.

	Remove a #define symbol that is no longer used from the
	ChipIdea host driver.

	Rename overrides to pci_overrides in ehci-pci.c, for
	consistency with ehci-platform.c.

	Mark the *_overrides structures as __initdata.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>