udf: move headers out include/linux/

There's really no reason to keep udf headers in include/linux as they're
not used by anything but fs/udf/.

This patch merges most of include/linux/udf_fs_i.h into fs/udf/udf_i.h,
include/linux/udf_fs_sb.h into fs/udf/udf_sb.h and
include/linux/udf_fs.h into fs/udf/udfdecl.h.

The only thing remaining in include/linux/ is a stub of udf_fs_i.h
defining the four user-visible udf ioctls.  It's also moved from
unifdef-y to headers-y because it can be included unconditionally now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index aada32f..897d84e 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -149,6 +149,7 @@
 header-y += tipc.h
 header-y += tipc_config.h
 header-y += toshiba.h
+header-y += udf_fs_i.h
 header-y += ultrasound.h
 header-y += un.h
 header-y += utime.h
@@ -336,7 +337,6 @@
 unifdef-y += timex.h
 unifdef-y += tty.h
 unifdef-y += types.h
-unifdef-y += udf_fs_i.h
 unifdef-y += udp.h
 unifdef-y += uinput.h
 unifdef-y += uio.h