tee_client_api: deprecate two TEE_ERROR_* macros not in the specification

TEE_ERROR_EXTERNAL_CANCEL and TEE_ERROR_STORAGE_NO_SPACE are not part
of the specification [1]. TEEC_ERROR_EXTERNAL_CANCEL and
TEEC_ERROR_STORAGE_NO_SPACE should be preferred instead.

Add a message in the description to deprecate these two macros, but
keep them for backward compatibility.

[1] TEE Client API Specification v1.0 Errata and Precisions
    Version 2.0, §P.4 Define Additional Return Codes

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Acked-by: Etienne Carriere <etienne.carriere@foss.st.com>