pci: write file size to inode on proc bus file write

When a /proc/bus/pci file is written to, the size of that PCI device's
configuration space must be written to the inode.  Otherwise, it is
possible for the file to specify a size of 0 on stat if a task is holding
the same file open.

Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>