hdspmixer - small memory leak fix

ALSA bug#3687
	https://bugtrack.alsa-project.org/alsa-bug/view.php?id=3687

the hdspmixer application leaks one memory block, a c-style string
which is obtained by snd_card_get_longname, but never freed ...

hdspmixer/src/hdspmixer.cxx

@@ -72,6 +72,7 @@ int main(int argc, char **argv)
 	    } 
 	}
     }
+    free(name);
     if (!cards) {
 	printf("No Hammerfall DSP card found.\n");
 	exit(EXIT_FAILURE);