net: designware: add clock support

This implementation manages several clocks, disable and
free all of them in case of error during probe and in remove
callback.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>