grandcentral: pass Curio DREQ state to its DMA channel.

Bit 5 of the channel status register of the SCSI0 DMA channel
reflects the DREQ signal from Curio.
The old SCSI API still used in some Macintosh applications
- most notably HD SC Setup and Drive Setup - relies on this API
and that signal to be implemented.

Author: maximumspatium

devices/ioctrl/grandcentral.cpp

@@ -126,6 +126,9 @@ GrandCentral::GrandCentral() : PCIDevice("mac-io/grandcentral"), InterruptCtrl()
     this->curio_dma = std::unique_ptr<DMAChannel> (new DMAChannel("curio_scsi"));
     this->curio_dma->register_dma_int(this, this->register_dma_int(IntSrc::DMA_SCSI_CURIO));
     this->curio->set_dma_channel(this->curio_dma.get());
+    this->curio->set_drq_callback([this](const uint8_t drq_state) {
+        this->curio_dma->set_stat((drq_state & 1) << 5);
+    });
 
     // connect Ethernet HW
     this->mace = dynamic_cast<MaceController*>(gMachineObj->get_comp_by_name("Mace"));