ARM: 6470/1: atomic64: use generic implementation for OABI configurations

The old apcs-gnu ABI doesn't guarantee that double words are allocated
to registers with even alignment, causing the 64-bit exclusive memory
operations to be rejected by the assembler.

This patch requires that CONFIG_AEABI is set in order to use the native
atomic operations and falls back to the generic (spinlock) code otherwise.
Acked-by: NNicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -6,7 +6,7 @@ config ARM
 	select HAVE_MEMBLOCK
 	select RTC_LIB
 	select SYS_SUPPORTS_APM_EMULATION
-	select GENERIC_ATOMIC64 if (!CPU_32v6K)
+	select GENERIC_ATOMIC64 if (!CPU_32v6K || !AEABI)
 	select HAVE_OPROFILE if (HAVE_PERF_EVENTS)
 	select HAVE_ARCH_KGDB
 	select HAVE_KPROBES if (!XIP_KERNEL)