kbuild: ignore *.order files

Introducing the new modules.order patch created a number
of additional files. Teach git to ignore them.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Tejun Heo <htejun@gmail.com>

.gitignore

@@ -17,6 +17,7 @@
 *.i
 *.lst
 *.symtypes
+*.order
 
 #
 # Top-level generic files