DSPHLE: Fix running and is_stream checks in AX HLE

A voice is considered running if and only if `running` equals 1,
not if `running` is not equal to 0.

This fixes https://bugs.dolphin-emu.org/issues/12508 because for some
reason *The Sims 2 - Castaway* sets `running` to 8 when a stream
finishes playing; previously our AX HLE would just loop the voice
and eventually crash after accessing invalid memory addresses.

Thanks to JMC47 and delroth's help, I've verified that this is the
correct check for the following ucodes:

GC:
* 0x3ad3b7ac
* 0x3daf59b9
* 0x4e8a8b21
* 0x07f88145
* 0xe2136399
* 0x3389a79e

Wii:
* 0x347112ba
* 0xfa450138
* 0xadbc06bd

And while I was fixing the running check, I noticed that the is_stream
field was also being handled incorrectly, so I've fixed that as well.

Source/Core/Core/HW/DSPHLE/UCodes/AXStructs.h

@@ -236,8 +236,8 @@ struct AXPB
   u16 coef_select;
   u16 mixer_control;
 
-  u16 running;    // 1=RUN 0=STOP
-  u16 is_stream;  // 1 = stream, 0 = one shot
+  u16 running;    // 1 = playing, anything else = stopped
+  u16 is_stream;  // 1 = stream, anything else = one shot
 
   PBMixer mixer;
   PBInitialTimeDelay initial_time_delay;

Source/Core/Core/HW/DSPHLE/UCodes/AXVoice.h

@@ -156,7 +156,7 @@ protected:
     {
       // Set the ADPCM info to continue processing at loop_addr.
       SetPredScale(acc_pb->adpcm_loop_info.pred_scale);
-      if (!acc_pb->is_stream)
+      if (acc_pb->is_stream != 1)
       {
         SetYn1(acc_pb->adpcm_loop_info.yn1);
         SetYn2(acc_pb->adpcm_loop_info.yn2);
@@ -403,7 +403,7 @@ void ProcessVoice(PB_TYPE& pb, const AXBuffers& buffers, u16 count, AXMixControl
                   const s16* coeffs)
 {
   // If the voice is not running, nothing to do.
-  if (!pb.running)
+  if (pb.running != 1)
     return;
 
   // Read input samples, performing sample rate conversion if needed.