ntfs3: Remove fsdata parameter from ntfs_extend_initialized_size()

ntfs3: Remove fsdata parameter from ntfs_extend_initialized_size()

After the last patch, Smatch reports:

        fs/ntfs3/file.c:168 ntfs_extend_initialized_size()
        error: uninitialized symbol 'fsdata'.

fsdata is indeed unused.  This is not new, but Smatch couldn't see it
before because calls through pagecache_write_begin()/pagecache_write_end()
could theoretically call any implemention of ->write_begin/write_end,
some of which do use fsdata.  Now that the calls are direct, Smatch can
see they're never used.

Fix this by simply passing NULL.  While ntfs3 does pass this parameter
on to generic functions, those generic functions also never dereference
the fsdata parameter, so it's unnecessary to pass the address of a real
pointer.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>