fs: fix inode.c kernel-doc warning

Fix kernel-doc warning in fs/inode.c:

..//fs/inode.c:1606: warning: No description found for parameter 'inode'

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