firmware: arm_scmi: Fix return error code in smc_send_message

SMCCC can return NOT_SUPPORTED(-1). Map it to appropriate Linux error
codes namely -EOPNOTSUPP.

Link: https://lore.kernel.org/r/20200417103232.6896-1-sudeep.holla@arm.com


Reported-and-Tested-by: : Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>