[MIPS] Ocelot G: Fix : "CURRENTLY_UNUSED" is not defined warning.

  CC      arch/mips/momentum/ocelot_g/gt-irq.o
arch/mips/momentum/ocelot_g/gt-irq.c:30:5: warning: "CURRENTLY_UNUSED" is not defined
arch/mips/momentum/ocelot_g/gt-irq.c:199:5: warning: "CURRENTLY_UNUSED" is not defined

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>