phy: Add USB3 PHY support for Broadcom NSP SoC

This patch adds support for Broadcom NSP USB3 PHY

Signed-off-by: Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@broadcom.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>