USB: Add DT probing support to ehci-spear and ohci-spear

This patch adds support to configure the SPEAr EHCI & OHCI driver via
device-tree instead of platform_data.

Signed-off-by: Stefan Roese <sr@denx.de>
Acked-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>