PCI/sysfs: Use default_groups in kobj_type for slot attrs

PCI/sysfs: Use default_groups in kobj_type for slot attrs

There are currently two ways to create a set of sysfs files for a
kobj_type: through the default_attrs field, and the default_groups field.
Move the PCI slot code to use the default_groups field which has been the
preferred way since aa30f47cf666 ("kobject: Add support for default
attribute groups to kobj_type") so that we can soon get rid of the obsolete
default_attrs field.

Link: https://lore.kernel.org/r/20211228135722.381023-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>