avutil/fixed_dsp: remove redundant cast

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/fixed_dsp.c

@@ -90,7 +90,7 @@ static void vector_fmul_window_fixed_c(int32_t *dst, const int32_t *src0,
 
 AVFixedDSPContext * avpriv_alloc_fixed_dsp(int bit_exact)
 {
-    AVFixedDSPContext * fdsp = (AVFixedDSPContext*)av_malloc(sizeof(AVFixedDSPContext));
+    AVFixedDSPContext * fdsp = av_malloc(sizeof(AVFixedDSPContext));
     fdsp->vector_fmul_window_scaled = vector_fmul_window_fixed_scaled_c;
     fdsp->vector_fmul_window = vector_fmul_window_fixed_c;