irqchip/loongson: Select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP for IRQ_LOONGARCH_CPU

An interrupt's effective affinity can only be different from its configured
affinity if there are multiple CPUs. Make it clear that this option is only
meaningful when SMP is enabled. Otherwise, there exists "WARNING: unmet
direct dependencies detected for GENERIC_IRQ_EFFECTIVE_AFF_MASK" when make
menuconfig if CONFIG_SMP is not set on LoongArch.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240326121130.16622-3-yangtiezhu@loongson.cn

drivers/irqchip/Kconfig

@@ -593,7 +593,7 @@ config IRQ_LOONGARCH_CPU
 	bool
 	select GENERIC_IRQ_CHIP
 	select IRQ_DOMAIN
-	select GENERIC_IRQ_EFFECTIVE_AFF_MASK
+	select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
 	select LOONGSON_HTVEC
 	select LOONGSON_LIOINTC
 	select LOONGSON_EIOINTC