Add disclaimer to README and update pdf manual

Change-Id: I19c957e5a1de9f87f1834d341221fad6c826b252

rocm_smi/docs/amd_smi_doxygen.cfg

@@ -909,7 +909,7 @@ FILTER_SOURCE_PATTERNS =
 # (index.html). This can be useful if you have a project on for instance GitHub
 # and want to reuse the introduction page also for the doxygen output.
 
-USE_MDFILE_AS_MAINPAGE = @CMAKE_CURRENT_SOURCE_DIR@/docs/ROCm_SMI_Intro.md
+USE_MDFILE_AS_MAINPAGE =
 
 #---------------------------------------------------------------------------
 # Configuration options related to source browsing