GPU: Allow DMAs in Mode 1

Exact behaviour is still unknown, but it works on console (Nicolas
Noble's torus demo).

src/core/gpu.h

@@ -116,7 +116,10 @@ public:
   // DMA access
   void DMARead(u32* words, u32 word_count);
 
-  ALWAYS_INLINE bool BeginDMAWrite() const { return (m_GPUSTAT.dma_direction == DMADirection::CPUtoGP0); }
+  ALWAYS_INLINE bool BeginDMAWrite() const
+  {
+    return (m_GPUSTAT.dma_direction == DMADirection::CPUtoGP0 || m_GPUSTAT.dma_direction == DMADirection::FIFO);
+  }
   ALWAYS_INLINE void DMAWrite(u32 address, u32 value)
   {
     m_fifo.Push((ZeroExtend64(address) << 32) | ZeroExtend64(value));