Add CMake generated config.h to gitignore

Prevent include/config.h, generated by CMake, from being in the
untracked files list.

Change-Id: I210be1137caadef7d3d74cc96b58e5cf30153472
Signed-off-by: Johnathan Mantey <johnathanx.mantey@intel.com>
diff --git a/.gitignore b/.gitignore
index 3ba693f..1f49091 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@
 *.key
 
 **/CMakeFiles/*
+/include/config.h