amrnb: use correct size when copying lsf_r array

lsf_r is an array of int16_t, not float.
Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/amrnbdec.c

@@ -255,7 +255,7 @@ static void lsf2lsp_for_mode12k2(AMRContext *p, double lsp[LP_FILTER_ORDER],
     }
 
     if (update)
-        memcpy(p->prev_lsf_r, lsf_r, LP_FILTER_ORDER * sizeof(float));
+        memcpy(p->prev_lsf_r, lsf_r, LP_FILTER_ORDER * sizeof(*lsf_r));
 
     for (i = 0; i < LP_FILTER_ORDER; i++)
         lsf_q[i] = lsf_r[i] * (LSF_R_FAC / 8000.0) + lsf_no_r[i] * (1.0 / 8000.0);