sysfs, kernfs: add skeletons for kernfs

Core sysfs implementation will be separated into kernfs so that it can
be used by other non-kobject users.

This patch creates fs/kernfs/ directory and makes boilerplate changes.
kernfs interface will be directly based on sysfs_dirent and its
forward declaration is moved to include/linux/kernfs.h which is
included from include/linux/sysfs.h.  sysfs core implementation will
be gradually separated out and moved to kernfs.

This patch doesn't introduce any functional changes.

v2: mount.c added.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --cc fs/Makefile
Simple merge

diff --cc fs/kernfs/Makefile
Simple merge

diff --cc fs/kernfs/dir.c
Simple merge

diff --cc fs/kernfs/file.c
Simple merge

diff --cc fs/kernfs/inode.c
Simple merge

diff --cc fs/kernfs/mount.c
Simple merge

diff --cc fs/kernfs/symlink.c
Simple merge

diff --cc include/linux/kernfs.h
Simple merge

diff --cc include/linux/sysfs.h
Simple merge