phy: add the ST ste10Xp PHYs

This patch adds the STMicroelectronics ste10xp PHY device driver.
It supports both the ste100p and the ste101p devices.

Suspend/resume alredy added.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>