ocfs2: Silence an error message in ocfs2_file_aio_read()

This patch silences an EINVAL error message in ocfs2_file_aio_read()
that is always due to a user error.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>