doc: update .PHONY to 2011

(cherry picked from commit 881fbe35477c1c360730b6bcc61e97e836ac3fe1)
Signed-off-by: Pierre Ynard <linkfanel@yahoo.fr>

doc/Makefile.am

@@ -67,7 +67,7 @@ $(CHANGELOGS): Makefile.am
 	fi
 
 # This one needs to be rebuilt all the time :)
-.PHONY: ChangeLog-2010 changelogs doc
+.PHONY: ChangeLog-2011 changelogs doc
 
 changelogs: $(CHANGELOGS)