USB:gadget:designware USB device controller (UDC) implementation

The earlier usb device controller driver was specific to spear platforms. This
patch implements the usb device controller driver as a generic controller which
can be reused by other platforms using this peripheral.

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
Signed-off-by: Amit Virdi <amit.virdi@st.com>
Acked-by: Marek Vasut <marex@denx.de>