net/designware: Program phy registers when auto-negotiation is ON

If AN(auto-negotiation) is ON, speed bit of control register are not
applicable.  Also phy registers were not getting programmed as per the
result of AN. This patch sets only AN bit & restart AN bit for AN ON
selection & programs PHY registers as per AN result.

Signed-off-by: Vikas Manocha <vikas.manocha@st.com>
Signed-off-by: Amit Virdi <amit.virdi@st.com>