[llvm-mca] Add an example showing how to get Intel assembly syntax

Patch by Jeff Muizelaar.

llvm-svn: 332627
diff --git a/llvm/docs/CommandGuide/llvm-mca.rst b/llvm/docs/CommandGuide/llvm-mca.rst
index d6324c8..e3e87a6 100644
--- a/llvm/docs/CommandGuide/llvm-mca.rst
+++ b/llvm/docs/CommandGuide/llvm-mca.rst
@@ -63,6 +63,12 @@
 
   $ clang foo.c -O2 -target x86_64-unknown-unknown -S -o - | llvm-mca -mcpu=btver2
 
+Or for Intel syntax:
+
+... code-block:: bash
+
+  $ clang foo.c -O2 -target x86_64-unknown-unknown -mllvm -x86-asm-syntax=intel -S -o - | llvm-mca -mcpu=btver2
+
 OPTIONS
 -------