ocfs2: Initialize count in aio_write before generic_write_checks

generic_write_checks() expects count to be initialized to the size of
the write.  Writes to files open with O_DIRECT|O_LARGEFILE write 0 bytes
because count is uninitialized.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.de>
Signed-off-by: Joel Becker <joel.becker@oracle.com>