Perform interrupt read flush as per serial open on BF1 devices.

driver-bitfury.c

@@ -29,6 +29,10 @@ static void bitfury_empty_buffer(struct cgpu_info *bitfury)
 
 static void bitfury_open(struct cgpu_info *bitfury)
 {
+	char buf[8];
+	int amount;
+
+	usb_read_ii(bitfury, 0, buf, 8, &amount, C_BF1_IFLUSH);
 	/* Magic open sequence */
 	usb_transfer(bitfury, 0x21, 0x22, 0x0003, 0, C_BF1_OPEN);
 	bitfury_empty_buffer(bitfury);

usbutils.h

@@ -335,6 +335,7 @@ struct cg_usb_info {
 	USB_ADD_COMMAND(C_BF1_GETWORK, "BF1GetWork") \
 	USB_ADD_COMMAND(C_BF1_GETRES, "BF1GetResults") \
 	USB_ADD_COMMAND(C_BF1_FLUSH, "BF1Flush") \
+	USB_ADD_COMMAND(C_BF1_IFLUSH, "BF1InterruptFlush") \
 	USB_ADD_COMMAND(C_BF1_IDENTIFY, "BF1Identify")
 
 /* Create usb_cmds enum from USB_PARSE_COMMANDS macro */