openldap: bump version to 2.4.43

- Bump version to 2.4.43
- Use md5 and sha1 upstream provided hashes. This combination is
  stronger than a sha256 hash.
- Switch to an http download site to avoid problems with firewalls
  blocking the ftp.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>