ecryptfs: super: Fix formatting, naming and kernel-doc abuses

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

 fs/ecryptfs/super.c:22: warning: cannot understand function prototype: 'struct kmem_cache *ecryptfs_inode_info_cache; '
 fs/ecryptfs/super.c:91: warning: Function parameter or member 'dentry' not described in 'ecryptfs_statfs'
 fs/ecryptfs/super.c:91: warning: Excess function parameter 'sb' description in 'ecryptfs_statfs'
 fs/ecryptfs/super.c:120: warning: Function parameter or member 'inode' not described in 'ecryptfs_evict_inode'
 fs/ecryptfs/super.c:133: warning: Function parameter or member 'm' not described in 'ecryptfs_show_options'
 fs/ecryptfs/super.c:133: warning: Function parameter or member 'root' not described in 'ecryptfs_show_options'

Cc: Tyler Hicks <code@tyhicks.com>
Cc: "Michael A. Halcrow" <mahalcro@us.ibm.com>
Cc: "Michael C. Thompson" <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>