denver: optimize memmove

Optimize 32-bit denver memmove with reversal memcpy.

Change-Id: Iaad0a9475248cdd7e4f50d58bea9db1b767abc88
diff --git a/libc/arch-arm/cortex-a15/cortex-a15.mk b/libc/arch-arm/cortex-a15/cortex-a15.mk
index d0896af..552811e 100644
--- a/libc/arch-arm/cortex-a15/cortex-a15.mk
+++ b/libc/arch-arm/cortex-a15/cortex-a15.mk
@@ -7,3 +7,4 @@
     arch-arm/cortex-a15/bionic/strlen.S \
     arch-arm/cortex-a15/bionic/__strcat_chk.S \
     arch-arm/cortex-a15/bionic/__strcpy_chk.S \
+    bionic/memmove.c \