arch/arm: always has atomic ops

armv6 and above all have one sort of atomic ops or another. For armv5
and below, they are emulated, either as a kernel trap, a kernel VDSO,
or compiler intrinsics.

Aarch64 is just armv8, so make it a single commit. ;-)

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.aarch64

@@ -3,3 +3,6 @@ config BR2_ARCH
 
 config BR2_ENDIAN
 	default "LITTLE"
+
+config BR2_ARCH_HAS_ATOMICS
+	default y

arch/Config.in.arm

@@ -340,6 +340,9 @@ config BR2_ENDIAN
 	default "LITTLE" if BR2_arm
 	default "BIG"	 if BR2_armeb
 
+config BR2_ARCH_HAS_ATOMICS
+	default y
+
 config BR2_GCC_TARGET_CPU
 	default "arm920"	if BR2_arm920
 	default "arm920t"	if BR2_arm920t