dirtyjtag: Allow custom VID/PID via command line options

Pass cable.vid and cable.pid to DirtyJtag constructor instead of using
hardcoded DIRTYJTAG_VID/PID. This allows users to use DirtyJTAG-compatible
firmware with custom USB VID/PID using the --vid and --pid flags:

  openFPGALoader -c dirtyJtag --vid 0x1337 --pid 0x0001 bitstream.fs

This is useful for custom DirtyJTAG implementations, embedded microcontrollers
with built-in JTAG adapters, or devices that use MS OS 2.0 descriptors for
automatic WinUSB driver loading with different VID/PID.

The default VID/PID (0x1209:0xC0CA) is preserved for backward compatibility.

src/jtag.cpp

@@ -139,7 +139,7 @@ Jtag::Jtag(const cable_t &cable, const jtag_pins_conf_t *pin_conf,
 		break;
 	case MODE_DIRTYJTAG:
 #ifdef ENABLE_DIRTYJTAG
-		_jtag = new DirtyJtag(clkHZ, verbose);
+		_jtag = new DirtyJtag(clkHZ, verbose, cable.vid, cable.pid);
 #else
 		std::cerr << "Jtag: support for dirtyJtag cable was not enabled at compile time" << std::endl;
 		throw std::exception();