ARM: tegra: harmony: update PCI-e initialization sequence

On Harmony board PCI-e subsystem can be enabled only after certain
voltage regulators are on. One of the regulators is an internal
regulator on the PMIC and another one is controlled by a PMIC GPIO.
Addition of the voltage control to the Harmony PCI-e initialization
allows booting of kernel with CONFIG_TEGRA_PCI even if the PMIC driver
is not loaded. In this case the PCI-e initialization will fail
gracefully intead of hanging the system.

Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Signed-off-by: Olof Johansson <olof@lixom.net>