buildroot

openntpd: update to 6.2p3

Other changes:

  - Remove upstream patch.
  - Change locally computed hash to hash from the SHA256 URL.
  - Add sha256sum for license file.

Note that we need to keep <pkg>_AUTORECONF = YES even though the patch
touching the Makefile.am has been removed, because our libtool patch
doesn't apply on the bundled ltmain.sh.

Signed-off-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>