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>

arch/openrisc/Kconfig

@@ -16,6 +16,7 @@ config OPENRISC
 	select GENERIC_IRQ_SHOW
 	select GENERIC_IOMAP
 	select GENERIC_CPU_DEVICES
+	select GENERIC_ATOMIC64
 
 config MMU
 	def_bool y