Fix return type of le64_to_cpu() and be64_to_cpu()

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/src/byteorder.h b/src/byteorder.h
index 5a8a64a..7362aeb 100644
--- a/src/byteorder.h
+++ b/src/byteorder.h
@@ -43,7 +43,7 @@
 static inline u32 le32_to_cpu(u32 x) {
     return x;
 }
-static inline u32 le64_to_cpu(u64 x) {
+static inline u64 le64_to_cpu(u64 x) {
     return x;
 }
 
@@ -62,7 +62,7 @@
 static inline u32 be32_to_cpu(u32 x) {
     return swab32(x);
 }
-static inline u32 be64_to_cpu(u64 x) {
+static inline u64 be64_to_cpu(u64 x) {
     return swab64(x);
 }