[docs] Update HTML pages to refer to CSS in a way that works locally and with Sphinx.

llvm-svn: 155153
diff --git a/llvm/docs/FAQ.html b/llvm/docs/FAQ.html
index 2a46a9e..5988809 100644
--- a/llvm/docs/FAQ.html
+++ b/llvm/docs/FAQ.html
@@ -5,7 +5,7 @@
   <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
   <title>LLVM: Frequently Asked Questions</title>
   <style type="text/css">
-    @import url("llvm.css");
+    @import url("_static/llvm.css");
     .question { font-weight: bold }
     .answer   { margin-left: 2em  }
   </style>