PCI/sysfs: Convert "reset" to static attribute

PCI/sysfs: Convert "reset" to static attribute

The "reset" sysfs attribute allows for resetting a PCI function.
Previously it was dynamically created either by pci_bus_add_device() or
the pci_sysfs_init() initcall, but since it doesn't need to be created or
removed dynamically, we can use a static attribute so the device model
takes care of addition and removal automatically.

Convert "reset" to a static attribute and use the .is_visible() callback to
check whether the device supports reset.

Clear reset_fn in pci_stop_dev() instead of pci_remove_capabilities_sysfs()
since we no longer explicitly remove the "reset" sysfs file.

[bhelgaas: commit log]
Suggested-by: Oliver O'Halloran <oohall@gmail.com>
Link: https://lore.kernel.org/r/20210416205856.3234481-4-kw@linux.com
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>