read target voltage first in vsllink

The very first command after init command should be "read target voltage".

This is a tweak for the Old Versaloon firmware.  Without this, in most
most cases, it works.   Under Ubuntu9.04, there is a chance that the USB
will fail.  The problem disappears if I read target voltage first.

For the lastest Versaloon firmware, it's OK.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

src/jtag/drivers/vsllink.c

@@ -476,6 +476,14 @@ static int vsllink_init(void)
 	}
 	VSLLINK_USB_TIMEOUT = to_tmp;
 
+	vsllink_simple_command(0x01);
+	result = vsllink_usb_read(vsllink_handle);
+	if (result != 2)
+		LOG_WARNING("Fail to get target voltage");
+	else
+		LOG_INFO("Target runs at %d mV", vsllink_usb_in_buffer[0]
+				+ (vsllink_usb_in_buffer[1] << 8));
+
 	// connect to vsllink
 	vsllink_connect();
 	// initialize function pointers