OpenRISC: Select GENERIC_ATOMIC64

To have atomit64_t on OpenRISC we need GENERIC_ATOMIC64.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Jonas Bonn <jonas@southpole.se>
diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index bc428b5..a478719 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -16,6 +16,7 @@
 	select GENERIC_IRQ_SHOW
 	select GENERIC_IOMAP
 	select GENERIC_CPU_DEVICES
+	select GENERIC_ATOMIC64
 
 config MMU
 	def_bool y