[.dir-locals.el] Add makefile-mode and asm-mode

For Makefile, tab is needed.
For .S file, tab is used. (one exception is shim/src/syscall.S, other .S uses tab)

.dir-locals.el

@@ -3,5 +3,7 @@
          (fill-column . 100)))
  (c-mode . ((c-file-style . "k&r")
             (c-basic-offset . 4)))
+ (makefile-mode . ((indent-tabs-mode . t)))
+ (asm-mode . ((indent-tabs-mode . t)))
  ((nil . ((truncate-lines . t)))
           (text-mode . ((eval . ((turn-on-auto-fill)))))))