libc: Enable high-performance memmove and bcopy for cortex-a15

Change-Id: Id8e4e595021dd13bf4ab5620f5fb0b0d80333616
libc: Unbreak build for scorpion

Use cortex-a15 memcpy and krait memset routines

Change-Id: I02cb178b33b01fc91e903f1f7b620640fd0f3310