Revert "OPDIS : Forgot to add sensible default for opdis_init!"

This reverts commit 43e0a8da86695bff458008b73f3ecc486aa73792.
Adding a parameter to opdis_init breaks compatibility. Users can always just
initialize the disassemble_info in the opdis_t manually.

Revert "OPDIS : Added an init_disassemble_info parameter to opdis_init()."

This reverts commit db4877280693baae0cc13a1ffca73ffd95381df7.