PCI: dwc: move dw_pcie_iatu_detect() after host_init callback

The commit 9ea48337 ("PCI: dwc: Move forward the iATU detection
process") broke PCIe support on Qualcomm SM8250 (and maybe other
platforms) since it moves the call to dw_pcie_iatu_detect() at the
beginning of the dw_pcie_host_init(), before ops->host_init() callback.
Accessing PCIe registers at this point causes the board to reboot since
not all clocks are enabled, making PCIe registers unavailable.

Move dw_pcie_iatu_detect() call after calling ops->host_init() callback,
so that all register are accessible.

Cc: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Fixes: 9ea48337 ("PCI: dwc: Move forward the iATU detection process")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>