ril: fix RIL_onUnsolicitedResponse

The header is mismatched. data shouldn't be const void*.

Fixes:
hardware/ril/libril/ril.cpp:3301:6: error: conflicting types for 'RIL_onUnsolicitedResponse'
void RIL_onUnsolicitedResponse(int unsolResponse, void *data,
     ^
hardware/ril/include/telephony/ril.h:4134:6: note: previous declaration is here
void RIL_onUnsolicitedResponse(int unsolResponse, const void *data,
     ^

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D588