phy: omap: Depend on OMAP_OCP2SCP bus driver

The OMAP_USB2 and OMAP_PIPE3 PHY devices will not be
detected if the OMAP_OCP2SCP bus driver is not present.
Make them depend on it.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>