optee: add error checks in optee_ffa_do_call_with_arg()

Adds error checking in optee_ffa_do_call_with_arg() for correctness.

Fixes: 4615e5a3

 ("optee: add FF-A support")
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>