libc: Add cortex-a53 bionic code

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

Change-Id: I1401b54b6c61d17782dff827d69f92b35a4f5c4f
Merge pull request #5 from CarbonDev/kk

libc: Add cortex-a53 bionic code