PCI: dwc: Move link handling into common code

PCI: dwc: Move link handling into common code

All the DWC drivers do link setup and checks at roughly the same time.
Let's use the existing .start_link() hook (currently only used in EP
mode) and move the link handling to the core code.

The behavior for a link down was inconsistent as some drivers would fail
probe in that case while others succeed. Let's standardize this to
succeed as there are usecases where devices (and the link) appear later
even without hotplug. For example, a reconfigured FPGA device.

Link: https://lore.kernel.org/r/20201105211159.1814485-11-robh@kernel.org
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Jingoo Han <jingoohan1@gmail.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Richard Zhu <hongxing.zhu@nxp.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>
Cc: Yue Wang <yue.wang@Amlogic.com>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Cc: Xiaowei Song <songxiaowei@hisilicon.com>
Cc: Binghui Wang <wangbinghui@hisilicon.com>
Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Stanimir Varbanov <svarbanov@mm-sol.com>
Cc: Pratyush Anand <pratyush.anand@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-omap@vger.kernel.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-amlogic@lists.infradead.org
Cc: linux-arm-kernel@axis.com
Cc: linux-arm-msm@vger.kernel.org
Cc: linux-tegra@vger.kernel.org