bib: Add reference for LKMM companion tests

Signed-off-by: Michalis Kokologiannakis <mixaskok@gmail.com>

biblio.bib

@@ -4323,6 +4323,16 @@
   urldate	= {2020-05-20}
 }
 
+@Misc{		  www:lkmm-tests,
+  key		= {lkmm-tests},
+  title		= {Automatically generated litmus tests for validation
+		  {LISA}-language {Linux-kernel} memory models},
+  author	= {Paul E. McKenney},
+  year		= {2021},
+  url		= {https://github.com/paulmckrcu/litmus},
+  urldate	= {2021-05-28}
+}
+
 @Misc{		  www:lli,
   key		= {lli},
   title		= {{lli} - directly execute programs from {LLVM} bitcode},