ecryptfs: main: Demote a bunch of non-conformant kernel-doc headers

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

 fs/ecryptfs/main.c:28: warning: Incorrect use of kernel-doc format:  * Module parameter that defines the ecryptfs_verbosity level.
 fs/ecryptfs/main.c:30: warning: cannot understand function prototype: 'int ecryptfs_verbosity = 0; '
 fs/ecryptfs/main.c:40: warning: cannot understand function prototype: 'unsigned int ecryptfs_message_buf_len = ECRYPTFS_DEFAULT_MSG_CTX_ELEMS; '
 fs/ecryptfs/main.c:52: warning: cannot understand function prototype: 'signed long ecryptfs_message_wait_timeout = ECRYPTFS_MAX_MSG_CTX_TTL / HZ; '
 fs/ecryptfs/main.c:65: warning: cannot understand function prototype: 'unsigned int ecryptfs_number_of_users = ECRYPTFS_DEFAULT_NUM_USERS; '
 fs/ecryptfs/main.c:106: warning: Function parameter or member 'dentry' not described in 'ecryptfs_init_lower_file'
 fs/ecryptfs/main.c:106: warning: Function parameter or member 'lower_file' not described in 'ecryptfs_init_lower_file'
 fs/ecryptfs/main.c:106: warning: Excess function parameter 'ecryptfs_dentry' description in 'ecryptfs_init_lower_file'
 fs/ecryptfs/main.c:244: warning: Function parameter or member 'sbi' not described in 'ecryptfs_parse_options'
 fs/ecryptfs/main.c:244: warning: Excess function parameter 'sb' description in 'ecryptfs_parse_options'
 fs/ecryptfs/main.c:478: warning: Function parameter or member 'fs_type' not described in 'ecryptfs_mount'
 fs/ecryptfs/main.c:478: warning: Function parameter or member 'flags' not described in 'ecryptfs_mount'
 fs/ecryptfs/main.c:478: warning: expecting prototype for ecryptfs_get_sb(). Prototype was for ecryptfs_mount() instead
 fs/ecryptfs/main.c:645: warning: Function parameter or member 'vptr' not described in 'inode_info_init_once'

Cc: Tyler Hicks <code@tyhicks.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: James Morris <jamorris@linux.microsoft.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>
[tyhicks: Correct the function documentation for ecryptfs_mount()]
Signed-off-by: Tyler Hicks <code@tyhicks.com>