package/libselinux: fix python module install patch

package/libselinux: fix python module install patch

Since commit 2768a0eb4 (package/libselinux: add dependency on
host-coreutils for ln --relative), we dropped a previous patch
which touched the same line, so the python module install patch
no longer applies.

Rather than drop use of ln --relative, which we now have (and
which was all that fuss was for), just drop the use of the PYCEXT
use altogether.

Fixes:
  - http://autobuild.buildroot.org/results/c8f/c8fe5b47e422bac13b4d5fa10bd1ee5218021585/ (host)
  - http://autobuild.buildroot.org/results/402/4026a34c6c096354ba99e8c202210428fa2795d2/ (target)

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Adam Duskett <aduskett@gmail.com>
Cc: Clayton Shotwell <clayton.shotwell@rockwellcollins.com>
Cc: Matt Weber <matthew.weber@rockwellcollins.com>
Cc: Marcus Folkesson <marcus.folkesson@gmail.com>
reviewed-by: Adam Duskett <aduskett@gmail.com>