crypto: scomp - Fix off-by-one bug when calculating last page

Fix off-by-one bug in the last page calculation for src and dst.

Reported-by: Nhat Pham <nphamcs@gmail.com>
Fixes: 2d3553ec ("crypto: scomp - Remove support for some non-trivial SG lists")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>