crypto: dcp - Staticize local symbols

These symbols are referenced only in this file and hence
should be static.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Tested-by: Tobias Rauter <tobiasrauter@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>