usb: ohci: remove ep93xx bus glue platform driver

Convert ep93xx to use the OHCI platform driver and remove the
ohci-ep93xx bus glue driver.

Enable CONFIG_OHCI_HCD_PLATFORM in the ep93xx_defconfig so that USB
is still enabled by default on the EP93xx platform.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>