crypto: caam - Staticize caam_jr_shutdown()

caam_jr_shutdown() is only used in this file, so it can be
made static.

This avoids the following sparse warning:

drivers/crypto/caam/jr.c:68:5: warning: symbol 'caam_jr_shutdown' was not declared. Should it be static?

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>