Fix perf regression on Cortex A15 by optimized memcpy for Cortex A9

The new Cortex A9 optimized memcpy included an arm-only version that is
slower than the current neon Cortex A15. This arm-only version was used
when the dst was aligned to an 8 byte boundary, otherwise, the original
neon only version was used. This change modifies the code so it always
uses the neon only version for the Cortex A15. It also fixes the use of
a define removed with the previous optimization.

Change-Id: I971527568a177218cd8b76a8bd160aaaf6ea1e42
Verify architecture neutral syscall numbers

Also removed some dead code and fixed comment

Change-Id: I5d6a04b4af3d95e34368136cf2eeb3c9b6f99769
Signed-off-by: Chris Dearman <chris@mips.com>
manual 4.2.2 merge