libselinux: bump to version 2.8

libselinux: bump to version 2.8

- Remove second patch (already in version), see
  https://github.com/SELinuxProject/selinux/commit/b24980ec07af66c4b419f8053aa65e97b36e558d
- Update third patch
- For target variant, set SHLIBDIR=/usr/lib because by default it is set
  to /lib and LIBDIR is set to $(PREFIX)/lib (with PREFIX=/usr)
- For host variant, set SHLIBDIR=$(HOST_DIR)/lib otherwise shared
  library will be installed in /lib (PREFIX is not used to install
  shared library)
- Add hash for license file

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>