arch/xtensa: always has atomic ops

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Anton Kolesov <Anton.Kolesov@synopsys.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

arch/Config.in.xtensa

@@ -35,3 +35,6 @@ config BR2_XTENSA_OVERLAY_DIR
 
 config BR2_ARCH
 	default "xtensa"	if BR2_xtensa
+
+config BR2_ARCH_HAS_ATOMICS
+	default y