iir: Change dst param to float* in ff_iir_filter_flt().

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit 69915b48)

libavcodec/iirfilter.c

@@ -269,7 +269,7 @@ void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
 
 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
                        struct FFIIRFilterState *s, int size,
-                       const float *src, int sstep, void *dst, int dstep)
+                       const float *src, int sstep, float *dst, int dstep)
 {
     if (c->order == 4) {
         FILTER_BW_O4(float, FLT)

libavcodec/iirfilter.h

@@ -117,6 +117,6 @@ void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterSta
  */
 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs,
                        struct FFIIRFilterState *state, int size,
-                       const float *src, int sstep, void *dst, int dstep);
+                       const float *src, int sstep, float *dst, int dstep);
 
 #endif /* AVCODEC_IIRFILTER_H */