ARM: v6k: select generic atomic64 code according to V6 variants

If CONFIG_CPU_V6 is enabled, avoid using the double-word exclusive
instructions in the kernel's atomic implementations as these are not
supported.  Fall back to the generic spinlock code instead.
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Tested-by: Sourav Poddar <sourav.poddar@ti.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -7,7 +7,7 @@ config ARM
 	select HAVE_MEMBLOCK
 	select RTC_LIB
 	select SYS_SUPPORTS_APM_EMULATION
-	select GENERIC_ATOMIC64 if (!CPU_32v6K || !AEABI)
+	select GENERIC_ATOMIC64 if (CPU_V6 || !CPU_32v6K || !AEABI)
 	select HAVE_OPROFILE if (HAVE_PERF_EVENTS)
 	select HAVE_ARCH_KGDB
 	select HAVE_KPROBES if (!XIP_KERNEL && !THUMB2_KERNEL)