The return value of one function is not properly documented

The function hsm_ctx_add_session is not returning the value that is described in the text above the function. The text for -1 is switched with the return value 1.

No calling function is checking whether the value is 1 or -1. They are just checking if the call was successful (0). So there is no problem caused by this. It is just that the documentation should be in sync with the code.