crypto: tegra-aes - Staticize tegra_aes_cra_exit

'tegra_aes_cra_exit' is used only in this file.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>