crypto: serpent-sse2/avx - allow both to be built into kernel

Rename serpent-avx assembler functions so that they do not collide with
serpent-sse2 assembler functions when linking both versions in to same
kernel image.

Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: Johannes Goetzfried <Johannes.Goetzfried@informatik.stud.uni-erlangen.de>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>