error_resilience: fix const correctness, silence warnings

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

libavcodec/error_resilience.c

@@ -236,7 +236,7 @@ static void h_block_filter(ERContext *s, uint8_t *dst, int w,
                            int h, int stride, int is_luma)
 {
     int b_x, b_y, mvx_stride, mvy_stride;
-    uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
+    const uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
     set_mv_strides(s, &mvx_stride, &mvy_stride);
     mvx_stride >>= is_luma;
     mvy_stride *= mvx_stride;
@@ -304,7 +304,7 @@ static void v_block_filter(ERContext *s, uint8_t *dst, int w, int h,
                            int stride, int is_luma)
 {
     int b_x, b_y, mvx_stride, mvy_stride;
-    uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
+    const uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
     set_mv_strides(s, &mvx_stride, &mvy_stride);
     mvx_stride >>= is_luma;
     mvy_stride *= mvx_stride;