core/crypto/crypto.c: fix compile errors when _CFG_CRYPTO_WITH_CIPHER=n
core/crypto/crypto.c: fix compile errors when _CFG_CRYPTO_WITH_CIPHER=n

Although _CFG_CRYPTO_WITH_CIPHER=n does not seem to be a valid
configuration (both the REE and RPMB FS use AES and at least one has to
be enabled currently), fix build errors triggered by:

  make _CFG_CRYPTO_WITH_CIPHER=n \
       out/arm-plat-vexpress/core/crypto/crypto.o

Signed-off-by: Jerome Forissier <ced78d268b4c9a0a20a59a9feeebd2ad90da03d3@linaro.org>
Reviewed-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>

pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os