Move memclr to a separate file to make it consistent
with other platforms asm function to file organization.

Remove nacl from the memmove filename as the implementation
is generic for the amd64p32 platform even if currently only
nacl is supported for amd64p32.

Change-Id: I8930b76da430a5cf2664801974e4f5185fc0f82f
Reviewed-on: https://go-review.googlesource.com/61031
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>