Port of a Linux commit 29d6b80

  The PCIe IP block has an additional clock, "pcie_aux", that needs to
  be controlled by the driver. Add code to support it.

  Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
  Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
  Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
  Cc: Bjorn Helgaas <bhelgaas@google.com>
  Cc: Fabio Estevam <fabio.estevam@nxp.com>
  Cc: Chris Healy <cphealy@gmail.com>
  Cc: Lucas Stach <l.stach@pengutronix.de>
  Cc: Leonard Crestez <leonard.crestez@nxp.com>
  Cc: "A.s. Dong" <aisheng.dong@nxp.com>
  Cc: Richard Zhu <hongxing.zhu@nxp.com>
  Cc: linux-imx@nxp.com
  Cc: linux-arm-kernel@lists.infradead.org
  Cc: linux-kernel@vger.kernel.org
  Cc: linux-pci@vger.kernel.org
  Cc: Rob Herring <robh@kernel.org>
  Cc: devicetree@vger.kernel.org

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>