Clanup media driver cmake config commands

[dvrogozh]

Looking to http://mediasdk.intel.com/buildbot/#builders/61/builds/2403:

[2020-09-16 07:49:26,036] media-driver: cmake INFO: cmd: cmake3 -DMEDIA_VERSION="19.4.0" -DCMAKE_INSTALL_PREFIX=/opt/intel/msdk_driver -DCMAKE_INSTALL_LIBDIR=/opt/intel/msdk_driver/lib64 -DINSTALL_DRIVER_SYSCONF=OFF -DLIBVA_DRIVERS_PATH=/opt/intel/msdk_driver/lib64 -DBUILD_TYPE=release -DENABLE_KERNELS=OFF /docker/worker/driver-kernels-off/build_dir/repos/media-driver

1. MEDIA_VERSION won't take any effect and is eventually wrong. Driver now comes with version in sources. If you want adjust it, you should use MEDIA_VERSION_EXTRA. See here:

https://github.com/intel/media-driver/blob/b285f47f1fb127cc3ca4f677631b6a71321a2db4/CMakeLists.txt#L23

2. Specifying LIBVA_DRIVERS_PATH is weird. This should be fetched automatically if you correctly configured and installed libva. Here is where it is taken into account in the driver code:
   media_driver/cmake/linux/media_include_paths_linux.cmake:33: pkg_get_variable(LIBVA_DRIVERS_PATH libva driverdir)