audio effects: fix heap overflow

Check consistency of effect command reply sizes before
copying to reply address.

Also add null pointer check on reply size.
Also remove unused parameter warning.

Bug: 21953516.
Change-Id: I4cf00c12eaed696af28f3b7613f7e36f47a160c4
(cherry picked from commit 0f714a464d2425afe00d6450535e763131b40844)

int32_t ReverbGetDiffusion(ReverbContext *pContext){

    LVREV_ControlParams_st    ActiveParams; /* Current control Parameters */
    LVREV_ReturnStatus_en     LvmStatus=LVREV_SUCCESS; /* Function call status */
    LVM_INT16                 Temp;

 /* Get the current settings */
 LvmStatus = LVREV_GetControlParameters(pContext->hInstance, &ActiveParams);
    LVM_ERROR_CHECK(LvmStatus, "LVREV_GetControlParameters", "ReverbGetDiffusion")

 Temp = (LVM_INT16)(pContext->SavedDiffusion/10);

 if(ActiveParams.Density != Temp){
        ALOGV("\tLVM_ERROR : ReverbGetDiffusion invalid value %d %d", Temp, ActiveParams.Density);
 }

 return pContext->SavedDiffusion;
}

int32_t ReverbGetDiffusion(ReverbContext *pContext){

    LVREV_ControlParams_st    ActiveParams; /* Current control Parameters */
    LVREV_ReturnStatus_en     LvmStatus=LVREV_SUCCESS; /* Function call status */
    LVM_INT16                 Temp;

 /* Get the current settings */
 LvmStatus = LVREV_GetControlParameters(pContext->hInstance, &ActiveParams);
    LVM_ERROR_CHECK(LvmStatus, "LVREV_GetControlParameters", "ReverbGetDiffusion")

 Temp = (LVM_INT16)(pContext->SavedDiffusion/10);

 if(ActiveParams.Density != Temp){
        ALOGV("\tLVM_ERROR : ReverbGetDiffusion invalid value %d %d", Temp, ActiveParams.Density);
 }

 return pContext->SavedDiffusion;
}
