PCI/sysfs: Define ACPI label attributes with DEVICE_ATTR*()

Use DEVICE_ATTR*() to simplify definitions of the ACPI label attributes.
No functional change intended.

[bhelgaas: split to separate patch]
Link: https://lore.kernel.org/r/20210416205856.3234481-6-kw@linux.com


Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>