Add upgrade sequence for r151040

Author: citrus-it

upgrade.md

@@ -23,6 +23,7 @@ The following table shows the supported upgrade paths between OmniOS versions.
 | r151032 (stable)		| →	| r151034, r151036 (stable), r151038 (LTS)
 | r151034 (stable)		| →	| r151036 (stable), r151038 (LTS)
 | r151036 (stable)		| →	| r151038 (LTS)
+| r151038 (LTS)			| →	| r151040 (stable)
 
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