usb: Move definition of USB_EHCI_BIG_ENDIAN_MMIO et al. out side of the ifs.

When CONFIG_USB_SUPPORT is not selected we get things like:

scripts/kconfig/mconf Kconfig
warning: (MIPS_SEAD3 && PMC_MSP && CPU_CAVIUM_OCTEON) selects USB_EHCI_BIG_ENDIAN_MMIO which has unmet direct dependencies (USB_SUPPORT && USB)

It is much cleaner to make the various system Kconfigs select
USB_EHCI_BIG_ENDIAN_MMIO rather than move the system config
information into USB's Kconfig, but the warnings are annoying.

Eliminate the warning by moving the definition of
USB_EHCI_BIG_ENDIAN_MMIO outside of all the Kconfig if statements.
While we are at it move USB_OHCI_BIG_ENDIAN_DESC,
USB_OHCI_BIG_ENDIAN_MMIO, USB_OHCI_LITTLE_ENDIAN and
USB_EHCI_BIG_ENDIAN_DESC too, as they could very well suffer similar
problems for other systems.

Get rid of the redundant "default n" in USB_OHCI_BIG_ENDIAN_DESC and
USB_OHCI_BIG_ENDIAN_MMIO

Signed-off-by: David Daney <david.daney@cavium.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>