PCI: imx6: Drop imx6_pcie_wait_for_link()

All calls to imx6_pcie_wait_for_link() share the same error path and
the state of PHY debug registers will already be printed there, so
there's no real reason we can't just use dw_pcie_wait_for_link(). Drop
imx6_pcie_wait_for_link() and replace it with dw_pcie_wait_for_link().

Suggested-by: Lucas Stach <l.stach@pengutronix.de>
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: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux-pci@vger.kernel.org