update CHANGELOG for release

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>

CHANGELOG.rst

@@ -7,6 +7,17 @@
 Change Log
 ==========
 
+[4.0.4] - 2019-10-21
+====================
+Changed
+-----
+- [sw] remove git dependency when building from SRPM
+- [sw] use Kbuild to build kernel module
+- [sw] remove wbgen2 requirement when bailing from SRPM
+Fixed
+-----
+- [sw] dkms is not a building requirement for RPM
+
 [4.0.3] - 2019-10-18
 ====================
 Changed