usb: phy: twl4030-usb: don't switch the phy on/off needlessly

With runtime_pm in place there is no longer need to turn the phy
on/off in OTG layer on cable connect/disconnect, OMAP glue does
this through otg.set_suspend() callback after it's called through
omap_musb_mailbox() on VBUS/ID interrupt. Not doing this will save
power when cable is connected but no gadget driver is loaded.

This will also have side effect of automatic USB charging no longer
working without twl4030_charger driver, because a regulator needed
for charging will no longer be enabled, so be sure to enable charger
driver if charging is needed.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>