[wwwdocs] readings.html -- update the link to blackfin docs

[Gerald Pfeifer]

Applied.

Gerald

Index: readings.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/readings.html,v
retrieving revision 1.307
diff -u -r1.307 readings.html
--- readings.html	1 Dec 2018 19:17:56 -0000	1.307
+++ readings.html	2 Dec 2018 10:54:13 -0000
@@ -93,7 +93,7 @@
 
  <li>Blackfin
   <br />Manufacturer: Analog Devices
-  <br /><a href="http://www.analog.com/en/products/processors-dsp/dsp/blackfin.html">Blackfin Documentation</a>
+  <br /><a href="https://www.analog.com/en/products/processors-dsp/dsp/blackfin.html">Blackfin Documentation</a>
  </li>
 
  <li>c4x