PCI: Use seq_puts() instead of seq_printf() in show_device()

The driver name in /proc/bus/pci/devices can be printed without a printf
format specification, so use seq_puts() instead of seq_printf().

This issue was detected by using the Coccinelle software.

Link: https://lore.kernel.org/r/a6b110cb-0d0e-5dc3-9ca1-9041609cf74c@web.de
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>