Blackfin: enable atomic64_t support

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index 01615d4..672c216 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -31,6 +31,7 @@
 	select HAVE_OPROFILE
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select HAVE_GENERIC_HARDIRQS
+	select GENERIC_ATOMIC64
 	select GENERIC_IRQ_PROBE
 	select IRQ_PER_CPU if SMP
 	select GENERIC_HARDIRQS_NO_DEPRECATED