include/linux/types.h: avoid duplicate definition of atomic64_t when 64BIT && GENERIC_ATOMIC64

If CONFIG_64BIT and CONFIG_GENERIC_ATOMIC64 are both y, atomic64_t is defined in both include/linux/types.h and include/asm-generic/atomic64.h. Allow the definition in include/asm-generic/atomic64.h to prevail, since that definition is consistent with the rest of CONFIG_GENERIC_ATOMIC64.

---
It does not appear that this is relevant to architectures that are in the kernel tree (i.e., no architectures use GENERIC_ATOMIC64 on 64-bit). It is relevant, however, to certain combinations of options for the RISC-V architecture currently in development.

Patch generated against 3.17-rc1.

 include/linux/types.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -177,7 +177,7 @@ typedef struct {
 	int counter;
 } atomic_t;
 
-#ifdef CONFIG_64BIT
+#if defined(CONFIG_64BIT) && !defined(CONFIG_GENERIC_ATOMIC64)
 typedef struct {
 	long counter;
 } atomic64_t;