powerpc/irq: use IS_ENABLED() in check_stack_overflow()

Instead of #ifdef, use IS_ENABLED(CONFIG_DEBUG_STACKOVERFLOW).
This enable GCC to check for code validity even when the option
is not selected.

Signed-off-by: Christophe Leroy <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/powerpc/kernel/irq.c

···
 
 static inline void check_stack_overflow(void)
 {
-#ifdef CONFIG_DEBUG_STACKOVERFLOW
 	long sp;
+
+	if (!IS_ENABLED(CONFIG_DEBUG_STACKOVERFLOW))
+		return;
 
 	sp = current_stack_pointer & (THREAD_SIZE - 1);
 
···
 		pr_err("do_IRQ: stack overflow: %ld\n", sp);
 		dump_stack();
 	}
-#endif
 }
 
 void __do_irq(struct pt_regs *regs)