ddimage: if 'pv' is installed, use it

This gives us a progress bar for the image write, which is quite helpful. See
https://www.ivarch.com/programs/pv.shtml.

(From OE-Core rev: 5b20cb2db929daaf0bf81c05368174e9c364ffab)

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/contrib/ddimage

@@ -100,5 +100,9 @@ if [ "$RESPONSE" != "y" ]; then
 fi
 
 echo "Writing image..."
-dd if="$IMAGE" of="$DEVICE" bs="$BLOCKSIZE"
+if which pv >/dev/null 2>&1; then
+	pv "$IMAGE" | dd of="$DEVICE" bs="$BLOCKSIZE"
+else
+	dd if="$IMAGE" of="$DEVICE" bs="$BLOCKSIZE"
+fi
 sync