SCI32: Allow changing SFX/speech volume in GK2

Originally, changing the SFX volume from ScummVM was disabled
because the game itself only allowed adjustment of music volume,
so adjusting the SFX volume would indirectly affect the music
volume. On reflection, allowing the adjustment of SFX volume even
though this also changes the music volume seems preferable to not
allowing any adjustment of the SFX/speech volumes.

engines/sci/detection_tables.h

@@ -843,9 +843,8 @@ static const struct ADGameDescription SciGameDescriptions[] = {
                             GUIO_NOLAUNCHLOAD, \
                             GUIO_NOASPECT, \
                             GAMEOPTION_HQ_VIDEO)
-#define GUIO_GK2      GUIO8(GUIO_NOSUBTITLES, \
-                            GUIO_NOSFX, \
-                            GUIO_NOSPEECHVOLUME, \
+#define GUIO_GK2      GUIO7(GUIO_NOSUBTITLES, \
+                            GUIO_LINKSPEECHTOSFX, \
                             GUIO_NOMIDI, \
                             GUIO_NOASPECT, \
                             GAMEOPTION_ORIGINAL_SAVELOAD, \