PCI: Increment PM usage counter when probing reset methods

We can get different results probing reset methods for a device depending
on its power state.  For example, reading the PM control register of a
device in D3cold will always indicate NoSoftRst+ because we get ~0 data
when the config read fails on PCI, preventing us from correctly probing PM
reset support.

Increment the PM usage counter before any probes and use the cleanup __free
facility to automatically drop the usage counter out of scope.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250422230534.2295291-3-alex.williamson@redhat.com