ecryptfs: inode: Help out nearly-there header and demote non-conformant ones

Fixes the following W=1 kernel build warning(s):

 fs/ecryptfs/inode.c:27: warning: Function parameter or member 'dentry' not described in 'lock_parent'
 fs/ecryptfs/inode.c:27: warning: Function parameter or member 'lower_dentry' not described in 'lock_parent'
 fs/ecryptfs/inode.c:27: warning: Function parameter or member 'lower_dir' not described in 'lock_parent'
 fs/ecryptfs/inode.c:27: warning: expecting prototype for eCryptfs(). Prototype was for lock_parent() instead
 fs/ecryptfs/inode.c:211: warning: Function parameter or member 'ecryptfs_dentry' not described in 'ecryptfs_initialize_file'
 fs/ecryptfs/inode.c:211: warning: Function parameter or member 'ecryptfs_inode' not described in 'ecryptfs_initialize_file'
 fs/ecryptfs/inode.c:258: warning: Function parameter or member 'mnt_userns' not described in 'ecryptfs_create'
 fs/ecryptfs/inode.c:258: warning: Function parameter or member 'directory_inode' not described in 'ecryptfs_create'
 fs/ecryptfs/inode.c:258: warning: Function parameter or member 'ecryptfs_dentry' not described in 'ecryptfs_create'
 fs/ecryptfs/inode.c:258: warning: Function parameter or member 'excl' not described in 'ecryptfs_create'
 fs/ecryptfs/inode.c:258: warning: Excess function parameter 'dir' description in 'ecryptfs_create'
 fs/ecryptfs/inode.c:258: warning: Excess function parameter 'dentry' description in 'ecryptfs_create'
 fs/ecryptfs/inode.c:320: warning: Function parameter or member 'dentry' not described in 'ecryptfs_lookup_interpose'
 fs/ecryptfs/inode.c:320: warning: Function parameter or member 'lower_dentry' not described in 'ecryptfs_lookup_interpose'
 fs/ecryptfs/inode.c:887: warning: Function parameter or member 'mnt_userns' not described in 'ecryptfs_setattr'

Cc: Tyler Hicks <code@tyhicks.com>
Cc: "Michael A. Halcrow" <mahalcro@us.ibm.com>
Cc: "Michael C. Thompsion" <mcthomps@us.ibm.com>
Cc: ecryptfs@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Tyler Hicks <code@tyhicks.com>