PCI: iproc: Enhance PCIe Link information display

Add logging code so that after successful linkup more comprehensive
information about PCIe link speed and link width will be displayed to
the console.

Link: https://lore.kernel.org/r/20201001060054.6616-4-srinath.mannam@broadcom.com
Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>