Revert "Bump SDK Extension version to 6"

This reverts commit b3b72e8910f123a0708752ed9d1dfb08dc57b966.

Reason for revert: Due to lack of testing extServices needs to deboard M-05 train and sdk finalization needs to be reverted

Change-Id: I278a499b5c30f13617c134ce27a43a8ffa32e099
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 3df3fb3..649032b 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -78,7 +78,7 @@
 .KATI_READONLY := PLATFORM_SDK_VERSION
 
 # This is the sdk extension version of this tree.
-PLATFORM_SDK_EXTENSION_VERSION := 6
+PLATFORM_SDK_EXTENSION_VERSION := 5
 .KATI_READONLY := PLATFORM_SDK_EXTENSION_VERSION
 
 # This is the sdk extension version that PLATFORM_SDK_VERSION ships with.