PCI: Clean-up MPS debug output

Clean-up MPS debug output to make it a single line and aligned, thus
making it more readable for a large number of buses and devices in a
single system.

Suggested by Benjamin Herrenschmidt <benh@kernel.crashing.org>

Signed-off-by: Jon Mason <mason@myri.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>