crypto: tcrpyt - Remove unnecessary kmap/kunmap calls

Noticed by Neil Horman: we are doing unnecessary kmap/kunmap calls
on kmalloced memory.  This patch removes them.  For the purposes of
testing SG construction, the underlying crypto code already does plenty
of kmap/kunmap calls anyway.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>