cifs: add a CIFSSMBQFileInfo function

...to get inode attributes via filehandle instead of by path.

In some places, we need to revalidate an inode on an open filehandle,
but we can't necessarily guarantee that the dentry associated with it
will still be valid. When we have an open filehandle already, it makes
more sense to do a filehandle based operation anyway.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>