AArch64: Fix flock64 for LP64.

On LP64 systems F_GETLK64, F_SETLK64 and F_SETLKW64 definitions should
map onto the F_GETLK, F_SETLK and F_SETLKW definitions, respectively.
LP64 also doesn't have a struct flock64.

Change-Id: Ibdfed9645d9e946999acd6efa8b96ea6238ed5bf
Signed-off-by: Marcus Oakland <marcus.oakland@arm.com>
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>
diff --git a/libc/include/fcntl.h b/libc/include/fcntl.h
index 779a089..cd68154 100644
--- a/libc/include/fcntl.h
+++ b/libc/include/fcntl.h
@@ -37,6 +37,20 @@
 
 __BEGIN_DECLS
 
+#ifdef __LP64__
+/* LP64 kernels don't have flock64 because their flock is 64-bit. */
+struct flock64 {
+  short l_type;
+  short l_whence;
+  off64_t l_start;
+  off64_t l_len;
+  pid_t l_pid;
+};
+#define F_GETLK64  F_GETLK
+#define F_SETLK64  F_SETLK
+#define F_SETLKW64 F_SETLKW
+#endif
+
 #ifndef O_ASYNC
 #define O_ASYNC  FASYNC
 #endif