[MIPS] Malta: Fix off by one bug in interrupt handler.

Fairly cosmetic as it would only affect VSMP / SMTC kernels that don't
use vectored interrupts.

Found by Beth.

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

arch/mips/mips-boards/malta/malta_int.c

@@ -256,7 +256,7 @@ asmlinkage void plat_irq_dispatch(void)
 
 	if (irq == MIPSCPU_INT_I8259A)
 		malta_hw0_irqdispatch();
-	else if (irq > 0)
+	else if (irq >= 0)
 		do_IRQ(MIPS_CPU_IRQ_BASE + irq);
 	else
 		spurious_interrupt();