Fix missing logging header installation

[OPNA2608]

The new header hasn't been added to the installed headers of the emu CMakeLists.txt. Without this, vgmplay-libvgm build errors out:

In file included from /build/source/playctrl.cpp:35:
/nix/store/wlaysm4d7zym0z9alr98q5mxj1zp6i4z-libvgm-unstable-2021-11-26-dev/include/vgm/player/droplayer.hpp:10:10: fatal error: ../emu/logging.h: No such file or directory
   10 | #include "../emu/logging.h"
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
In file included from /build/source/mediainfo.cpp:14:
/nix/store/wlaysm4d7zym0z9alr98q5mxj1zp6i4z-libvgm-unstable-2021-11-26-dev/include/vgm/player/droplayer.hpp:10:10: fatal error: ../emu/logging.h: No such file or directory
   10 | #include "../emu/logging.h"
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [CMakeFiles/vgmplay.dir/build.make:146: CMakeFiles/vgmplay.dir/playctrl.cpp.o] Error 1

[ValleyBell]

oops - thanks for fixing!