USB: remove USB_EHCI_BIG_ENDIAN_{DESC,MMIO} depends on architecture symbol

Just like the OHCI counter part we just can remove the architecture
specific symbols which prevent these configuration symbols from being
selected by platforms/architectures requiring it. The original
implementation did not scale at all since it required each and every
single architecture to be added for these configuration symbols to be
selected. Now it is up to the EHCI driver and/or platform to select
these configuration symbols accordingly.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/powerpc/platforms/512x/Kconfig

@@ -7,6 +7,8 @@ config PPC_MPC512x
 	select PPC_PCI_CHOICE
 	select FSL_PCI if PCI
 	select ARCH_WANT_OPTIONAL_GPIOLIB
+	select USB_EHCI_BIG_ENDIAN_MMIO
+	select USB_EHCI_BIG_ENDIAN_DESC
 
 config MPC5121_ADS
 	bool "Freescale MPC5121E ADS"