dw_pcie_ep_init() depends on the detected iATU region numbers to allocate
the in/outbound window management bitmap.  It fails after 281f1f99
("PCI: dwc: Detect number of iATU windows").

Move the iATU region detection into a new function, move the detection to
the very beginning of dw_pcie_host_init() and dw_pcie_ep_init().  Also
remove it from the dw_pcie_setup(), since it's more like a software
initialization step than hardware setup.

Link: https://lore.kernel.org/r/20210125044803.4310-1-Zhiqiang.Hou@nxp.com
Link: https://lore.kernel.org/linux-pci/20210407131255.702054-1-dmitry.baryshkov@linaro.org
Link: https://lore.kernel.org/r/20210413142219.2301430-1-dmitry.baryshkov@linaro.org
Fixes: 281f1f99 ("PCI: dwc: Detect number of iATU windows")
Tested-by: NKunihiko Hayashi <hayashi.kunihiko@socionext.com>
Tested-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Tested-by: NManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: NHou Zhiqiang <Zhiqiang.Hou@nxp.com>
[DB: moved dw_pcie_iatu_detect to happen after host_init callback]
Signed-off-by: NDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Cc: stable@vger.kernel.org	# v5.11+
Cc: Marek Szyprowski <m.szyprowski@samsung.com>