usb: phy: twl4030-usb: Move code from twl4030_phy_power to the runtime PM calls

We don't need twl4030_phy_power() any longer now that we have
the runtime PM calls. Let's get rid of it as it's confusing.
No functional changes, just move the code and use res instead
of ret as we are not returning that value.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>