PCI: dwc: Move N_FTS setup to common setup

The Designware controller has common registers to set number of fast
training sequence ordered sets. The Artpec6, Intel, and Tegra driver
initialize these register fields. Let's move the initialization to the
common setup code and drivers just have to provide the value.

There's a slight change in that the common clock mode N_FTS field is
now initialized. Previously only the Intel driver set this. It's not
clear from the code if common clock mode is used in the Artpec6 or Tegra
driver. It depends on the DWC configuration. Given the field is not
initialized while the others are, it seems unlikely common clock mode
is used.

Link: https://lore.kernel.org/r/20200821035420.380495-40-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: linux-tegra@vger.kernel.org