roi_harness: add README info, chmod +x

Signed-off-by: John McMaster <johndmcmaster@gmail.com>

minitests/roi_harness/README.txt

diff --git a/minitests/roi_harness/README.txt b/minitests/roi_harness/README.txt
index 2f24f2d..c81a5ad 100644
--- a/minitests/roi_harness/README.txt
+++ b/minitests/roi_harness/README.txt
@@ -17,3 +17,7 @@
 To build a sample Vivado design using the harness:
 XRAY_ROIV=roi_inv.v XRAY_FIXED_XDC=out_xc7a35tcpg236-1_BASYS3-SWBUT_roi_basev/fixed_noclk.xdc ./runme.sh
 Note: this was intended for verification only and not as an end user flow (they should use SymbiFlow)
+
+To use the harness for the basys3 demo, do something like:
+python3 demo_sw_led.py out_xc7a35tcpg236-1_BASYS3-SWBUT_roi_basev 3 2
+This example connects switch 3 to LED 2

minitests/roi_harness/demo_sw_led.py

diff --git a/minitests/roi_harness/demo_sw_led.py b/minitests/roi_harness/demo_sw_led.py
old mode 100644
new mode 100755

minitests/roi_harness/demo_sw_led_fasm.py

diff --git a/minitests/roi_harness/demo_sw_led_fasm.py b/minitests/roi_harness/demo_sw_led_fasm.py
old mode 100644
new mode 100755

minitests/roi_harness/test_demo_sw_led.py

diff --git a/minitests/roi_harness/test_demo_sw_led.py b/minitests/roi_harness/test_demo_sw_led.py
old mode 100644
new mode 100755