PCI/VGA: Use unsigned format string to print lock counts

In struct vga_device, io_lock_cnt and mem_lock_cnt are unsigned, but we
previously printed them with "%d", the signed decimal format.  Print them
with the unsigned format "%u" instead.

Link: https://lore.kernel.org/r/20220224224753.297579-11-helgaas@kernel.org


Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>