cifs: Replace remaining 1-element arrays

The kernel is globally removing the ambiguous 0-length and 1-element
arrays in favor of flexible arrays, so that we can gain both compile-time
and run-time array bounds checking[1].

Replace the trailing 1-element array with a flexible array in the
following structures:

	struct cifs_spnego_msg
	struct cifs_quota_data
	struct get_dfs_referral_rsp
	struct file_alt_name_info
	NEGOTIATE_RSP
	SESSION_SETUP_ANDX
	TCONX_REQ
	TCONX_RSP
	TCONX_RSP_EXT
	ECHO_REQ
	ECHO_RSP
	OPEN_REQ
	OPENX_REQ
	LOCK_REQ
	RENAME_REQ
	COPY_REQ
	COPY_RSP
	NT_RENAME_REQ
	DELETE_FILE_REQ
	DELETE_DIRECTORY_REQ
	CREATE_DIRECTORY_REQ
	QUERY_INFORMATION_REQ
	SETATTR_REQ
	TRANSACT_IOCTL_REQ
	TRANSACT_CHANGE_NOTIFY_REQ
	TRANSACTION2_QPI_REQ
	TRANSACTION2_SPI_REQ
	TRANSACTION2_FFIRST_REQ
	TRANSACTION2_GET_DFS_REFER_REQ
	FILE_UNIX_LINK_INFO
	FILE_DIRECTORY_INFO
	FILE_FULL_DIRECTORY_INFO
	SEARCH_ID_FULL_DIR_INFO
	FILE_BOTH_DIRECTORY_INFO
	FIND_FILE_STANDARD_INFO

Replace the trailing 1-element array with a flexible array, but leave
the existing structure padding:

	FILE_ALL_INFO
	FILE_UNIX_INFO

Remove unused structures:

	struct gea
	struct gealist

Adjust all related size calculations to match the changes to sizeof().

No machine code output differences are produced after these changes.

[1] For lots of details, see both:
    https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays
    https://people.kernel.org/kees/bounded-flexible-arrays-in-c



Cc: Steve French <sfrench@samba.org>
Cc: Paulo Alcantara <pc@cjr.nz>
Cc: Ronnie Sahlberg <lsahlber@redhat.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Steve French <stfrench@microsoft.com>