USB: Add support for OHCI controller on S3C6400

Notice: USB on S3C6400 currently works _only_ with switched off MMU. One could
try to enable the MMU, but map addresses 1-to-1, and disable data cache, then
it should work too and we could still profit from instruction cache.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>