alpha: make short build log available for division routines

This enables the Kbuild standard log style as follows:

  AS      arch/alpha/lib/__divlu.o
  AS      arch/alpha/lib/__divqu.o
  AS      arch/alpha/lib/__remlu.o
  AS      arch/alpha/lib/__remqu.o

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>