access_output_tts: return -1 for init error

access_output_tts: return -1 for init error

The return value of elm_modapi_init is used by _access_init in elementary.
If the return value is negative, it means the init is not done correctly.
So elm_modapi_init should have to return negative value if there is a porblem.

If elm_modapi_init uses the return value of TTS api as a return value,
and the TTS api return value is not negative even though there is an error,
then elementary regards that there is not a problem, and will not try to
init access_output_tts module again.

Change-Id: I941d9ad24f36e27f91d07884991725aa45b2a790