phy: rcar-gen3-usb2: fix implementation for runtime PM

This patch fixes an issue that this driver doesn't take care of the runtime
PM. This code assumed that devm_phy_create() called pm_runtime_enable(dev),
but it misunderstood the dev_phy_create()'s specification.
This driver should call its own pm_runtime_enable() before
dev_phy_create().

Fixes: f3b5a8d9 ("phy: rcar-gen3-usb2: Add R-Car Gen3 USB2 PHY driver")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>