libc: Add cortex-a53 bionic code

Add cortex-a53 makefile. Currently it
uses cortex-a15 bionic code.

Change-Id: I1401b54b6c61d17782dff827d69f92b35a4f5c4f
diff --git a/libc/arch-arm/cortex-a53/cortex-a53.mk b/libc/arch-arm/cortex-a53/cortex-a53.mk
new file mode 100644
index 0000000..9af03d9
--- /dev/null
+++ b/libc/arch-arm/cortex-a53/cortex-a53.mk
@@ -0,0 +1 @@
+include bionic/libc/arch-arm/cortex-a15/cortex-a15.mk