ia64: beatify build log for gate.so and gate-syms.o

Currently, the object path is not aligned in the build log:

  LDS     arch/ia64/kernel/gate.lds
  AS      arch/ia64/kernel/gate.o
  GATE arch/ia64/kernel/gate.so
  AS      arch/ia64/kernel/gate-data.o
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>