core: ltc: DSA signature verification: fix return code
core: ltc: DSA signature verification: fix return code

The GP TEE Internal Core specification mandates that
TEE_AsymmetricVerifyDigest() must return TEE_SUCCESS if the signature
is valid, TEE_ERROR_SIGNATURE_INVALID if it is invalid, or panic if any
other error oocurs.

In the current implementation, TEE_ERROR_SIGNATURE_INVALID will never
happen with the DSA algorithms. Fix that by properly checking the
return code and signature status of the LibTomCrypt function.

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