9p: make v9fs_cache_inode_{get,put,set}_cookie empty inlines for !9P_CACHEFS

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/9p/cache.h
Simple merge

diff --cc fs/9p/vfs_file.c
Simple merge

diff --cc fs/9p/vfs_inode.c
Simple merge

diff --cc fs/9p/vfs_inode_dotl.c
Simple merge