pci: pcie_dw_meson: Use dw_pcie_link_set_max_link_width()

pci: pcie_dw_meson: Use dw_pcie_link_set_max_link_width()

Use dw_pcie_link_set_max_link_width() instead of local implementation
of the same functionality. This does change the behavior slightly, as
the dw_pcie_link_set_max_link_width() implementation also programs the
LNKCAP register MLW, this should however be correct and is now aligned
with Linux kernel behavior.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>