SCI32: Return CD speed in kPlatform

This fixes missing playback of some videos in Rama, like the
background video that plays when selecting an email at the
computer at the start of the game.

engines/sci/engine/kmisc.cpp

@@ -647,6 +647,9 @@ reg_t kPlatform32(EngineState *s, int argc, reg_t *argv) {
 	case kGetColorDepth:
 		return make_reg(0, /* 256 color */ 2);
 	case kGetCDSpeed:
+		// The value `4` comes from Rama DOS resource.cfg installed in DOSBox,
+		// and seems to correspond to the highest expected CD speed value
+		return make_reg(0, 4);
 	case kGetCDDrive:
 	default:
 		return NULL_REG;