cuda: don't call cuda_update() when writing to ACR register

The wire protocol for reading data to/from the VIA is triggered by changing
inputs on port B rather than changing the timer configuration via the ACR.
Signed-off-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

hw/misc/macio/cuda.c

@@ -407,7 +407,6 @@ static void cuda_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
     case CUDA_REG_ACR:
         s->acr = val;
         cuda_timer_update(s, &s->timers[0], qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
-        cuda_update(s);
         break;
     case CUDA_REG_PCR:
         s->pcr = val;