Documentation/kernel-docs.txt: add two published books

Add two books from my own bookshelf. I found them useful by
the time I bought; so it could be useful to others ;)

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/kernel-docs.txt

@@ -476,6 +476,14 @@ Published books
       :Pages: 648
       :ISBN: 978-1430261964
 
+    * Title: **Embedded Linux Primer: A practical Real-World Approach, 2nd Edition**
+
+      :Author: Christopher Hallinan
+      :Publisher: Pearson
+      :Date: November, 2010
+      :Pages: 656
+      :ISBN: 978-0137017836
+
     * Title: **Linux Kernel Development, 3rd Edition**
 
       :Author: Robert Love
@@ -484,6 +492,14 @@ Published books
       :Pages: 440
       :ISBN: 978-0672329463
 
+    * Title: **Essential Linux Device Drivers**
+
+      :Author: Sreekrishnan Venkateswaran
+      :Published: Prentice Hall
+      :Date: April, 2008
+      :Pages: 744
+      :ISBN: 978-0132396554
+
 .. _ldd3_published:
 
     * Title: **Linux Device Drivers, 3rd Edition**