vfs: make first argument of dir_context.actor typed

arch/alpha/kernel/osf_sys.c

arch/parisc/hpux/fs.c

drivers/staging/lustre/lustre/llite/llite_nfs.c

fs/afs/dir.c

fs/compat.c

fs/ecryptfs/file.c

fs/exportfs/expfs.c

fs/fat/dir.c

fs/gfs2/export.c

fs/hppfs/hppfs.c

fs/nfsd/nfs4recover.c

fs/nfsd/vfs.c

fs/nfsd/vfs.h

fs/ocfs2/dir.c

fs/ocfs2/journal.c

fs/overlayfs/readdir.c

fs/readdir.c

fs/reiserfs/xattr.c

include/linux/fs.h