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)

static inline int16_t clamp16(int32_t sample)
{
 if ((sample>>15) ^ (sample>>31))
        sample = 0x7FFF ^ (sample>>31);
 return sample;
}

static inline int16_t clamp16(int32_t sample)
{
 if ((sample>>15) ^ (sample>>31))
        sample = 0x7FFF ^ (sample>>31);
 return sample;
}
