MIPS: Define __arch_swab64 for all mips r2 cpus

Some CPUs implement mipsr2, but because they are a super-set of mips64r2 do
not define CONFIG_CPU_MIPS64_R2.  Cavium OCTEON falls into this category.
We would still like to use the optimized implementation, so since we have
already checked for CONFIG_CPU_MIPSR2, checking for CONFIG_64BIT instead of
CONFIG_CPU_MIPS64_R2 is sufficient.
Signed-off-by: NDavid Daney <ddaney@caviumnetworks.com>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/swab.h

@@ -38,7 +38,11 @@ static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
 }
 #define __arch_swab32 __arch_swab32
 
-#ifdef CONFIG_CPU_MIPS64_R2
+/*
+ * Having already checked for CONFIG_CPU_MIPSR2, enable the
+ * optimized version for 64-bit kernel on r2 CPUs.
+ */
+#ifdef CONFIG_64BIT
 static inline __attribute_const__ __u64 __arch_swab64(__u64 x)
 {
 	__asm__(
@@ -50,6 +54,6 @@ static inline __attribute_const__ __u64 __arch_swab64(__u64 x)
 	return x;
 }
 #define __arch_swab64 __arch_swab64
-#endif /* CONFIG_CPU_MIPS64_R2 */
+#endif /* CONFIG_64BIT */
 #endif /* CONFIG_CPU_MIPSR2 */
 #endif /* _ASM_SWAB_H */