phy: ti-pipe3: use *syscon* framework API to power on/off the PHY

Deprecate using phy-omap-control driver to power on/off the PHY and
use *syscon* framework to do the same.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Acked-by: Rob Herring <robh@kernel.org>