arch/optee: add scmi_configure() prototype

This function is called by OP-TEE before arch_main_init() to configure
dynamically SCP-Fw resources.

OP-TEE parse "scmi" device-tree node to fill the scpfw_config structure
with SCMI resources before calling scmi_configure(). In "scmi" node,
all SCMI resources are described, sorted by protocol, and for each agent.

scpfw_config structure is defined in OP-TEE:
core/lib/scmi-server/include/scmi_agent_configuration.h

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>