Update ffado so ffado-mixer doesn't depend on Qt4 which will be removed soon (boo#1179613)

- update to release 2.4.3
- removed unneeded Patch (fixed upstream):
ffado-mixer-fixbuild.patch

- Replace pkgconfig(libxml++-2.6) with pkgconfig(libxml++-3.0)
BuildRequires.

- Change Buildrequires: pkgconfig(dbus-python-3.6) back to the plain
python3-dbus-python-devel package, pkgconfig is no longer provided.

- Update to release 2.4.1
- Fix build with ffado-mixer-fixbuild.patch.
- Removed uneeded and incorporated patches:
libffado-SConstruct-py3.patch, ffado-gcc6.patch and byteswap.patch
- Upstream changes:
*Fix some python syntax which was not compatible with python3.
These were missed during the preparation of FFADO 2.4.0.
*Modify the SCons build system to allow for scons running under
python3.
*Merge distribution patches provided by package maintainers.
*Address some difficulties experienced by package maintainers
when compiling FFADO.
*Improve the output of ffado-diag.

- byteswap.patch: ensure byte swap macros are available for all components

- Update to release 2.4.0 and fix build against glibc-2.27
see boo#1079938.
- Removed patches fixed upstream:
ffado_SConstruct_powerpc_update.patch and sigev.patch.