Add faster, architecture dependent memcpy()

Add faster, architecture dependent memcpy()

Change-Id: I38d15f3f1ec65f0cb7974d2dd4ae6356433bddd8
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: http://review.coreboot.org/736
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins)