gus: clean up MemoryRegionPortio

Remove 16-bit reads/writes, since ioport.c is able to synthesize them.
Remove the two MIDI registers (0x300 and 0x301) from gus_portio_list1,
and add the second MIDI register (0x301) to gus_portio_list2.

Tested with Second Reality.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/audio/gus.c

@@ -71,27 +71,13 @@ IO_READ_PROTO (gus_readb)
     return gus_read (&s->emu, nport, 1);
 }
 
-IO_READ_PROTO (gus_readw)
-{
-    GUSState *s = opaque;
-
-    return gus_read (&s->emu, nport, 2);
-}
-
 IO_WRITE_PROTO (gus_writeb)
 {
     GUSState *s = opaque;
 
     gus_write (&s->emu, nport, 1, val);
 }
 
-IO_WRITE_PROTO (gus_writew)
-{
-    GUSState *s = opaque;
-
-    gus_write (&s->emu, nport, 2, val);
-}
-
 static int write_audio (GUSState *s, int samples)
 {
     int net = 0;
@@ -236,17 +222,13 @@ static const VMStateDescription vmstate_gus = {
 
 static const MemoryRegionPortio gus_portio_list1[] = {
     {0x000,  1, 1, .write = gus_writeb },
-    {0x000,  1, 2, .write = gus_writew },
     {0x006, 10, 1, .read = gus_readb, .write = gus_writeb },
-    {0x006, 10, 2, .read = gus_readw, .write = gus_writew },
     {0x100,  8, 1, .read = gus_readb, .write = gus_writeb },
-    {0x100,  8, 2, .read = gus_readw, .write = gus_writew },
     PORTIO_END_OF_LIST (),
 };
 
 static const MemoryRegionPortio gus_portio_list2[] = {
-    {0, 1, 1, .read = gus_readb },
-    {0, 1, 2, .read = gus_readw },
+    {0, 2, 1, .read = gus_readb },
     PORTIO_END_OF_LIST (),
 };