sh: Convert to USB_ARCH_HAS_OHCI/EHCI selects.

This switches over to selects for the subtypes to enable OHCI/EHCI
support explicitly rather than littering the usb Kconfig with subtype
dependencies.

Suggested-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>