Small cleanup of cortex-a15 code.

Remove new version of the cortex-a15 that caused a regression. We are never
going to revisit that code, and it is only confusing things.

Also remove the setting of MEMCPY_BASE and use the correct include
directly.

Test: Compiled angler with 32 bit arch as cortex-a15. Ran 32 bit bionic
Test: unit tests on angler.

Change-Id: I9372c01758fd7a596849c87b1a3f805bb477c94f