phy: marvell: add comphy type PHY_TYPE_USB3

- For some Marvell SoCs, like armada-3700, there are both
  USB host and device controller, but on PHY level the
  configuration is the same.
- The new type supports both USB device and USB host
- This patch is cherry-picked from u-boot-2015 as-is.

Change-Id: I01262027edd8ec23391cff6fb409b3009aedfbb9
Signed-off-by: jinghua <jinghua@marvell.com>
Signed-off-by: Ken Ma <make@marvell.com>
Reviewed-by: Igal Liberman <igall@marvell.com>