vp8 fix: deallocate denoiser->yv12_last_source

Change-Id: I7f3bc292b1b411e10586f0975143ae996ea78d1d

vp8/encoder/denoising.c

@@ -430,6 +430,7 @@ void vp8_denoiser_free(VP8_DENOISER *denoiser)
         vp8_yv12_de_alloc_frame_buffer(&denoiser->yv12_running_avg[i]);
     }
     vp8_yv12_de_alloc_frame_buffer(&denoiser->yv12_mc_running_avg);
+    vp8_yv12_de_alloc_frame_buffer(&denoiser->yv12_last_source);
     vpx_free(denoiser->denoise_state);
 }