LoongArch: Select HAVE_CMPXCHG_LOCAL in Kconfig

LoongArch has already implemented cmpxchg_local(), this_cpu_cmpxchg()
and similar functions, so select HAVE_CMPXCHG_LOCAL in Kconfig to avoid
incurring the overhead of local_irq_save()/local_irq_restore() for page
state helpers in mm/vmstat.c.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/Kconfig

@@ -130,6 +130,7 @@ config LOONGARCH
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD
 	select HAVE_ASM_MODVERSIONS
+	select HAVE_CMPXCHG_LOCAL
 	select HAVE_CONTEXT_TRACKING_USER
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_DEBUG_KMEMLEAK