package/faifa: fix incorrect library symlink

As spotted in
http://autobuild.buildroot.net/results/a61/a612cb7a85927d8cfe55c95c34d2901e7694fab0//diffoscope-results.txt

,
faifa installs a library symlink with an incorrect target, which was
detected by the reproducible build logic, but is in fact wrong in any
case:

-lrwxrwxrwx   0        0        0        0 2019-11-07 19:38:04.000000 ./usr/lib/libfaifa.so -> /home/naourr/work/instance-3/output-1/target/usr/lib/libfaifa.so.0
+lrwxrwxrwx   0        0        0        0 2019-11-07 19:38:04.000000 ./usr/lib/libfaifa.so -> /home/naourr/work/instance-3/output-2/target/usr/lib/libfaifa.so.0

In practice, this is not a problem at runtime, as the .so symlink is
not used: the library soname is libfaifa.so.0. However, it still makes
sense to fix.

It is fixed by backporting an upstream commit. We considered bumping
to a newer version, but the latest version requires a new dependency
(libevent), so we preferred the backporting approach.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>