Correct confusing not-a-bug in CDEF bounds

Block boundary calculation is correct by accident-- make it correct on purpose.

src/cdef.rs

@@ -257,8 +257,8 @@ pub fn cdef_filter_superblock(fi: &FrameInvariants,
     // Each direction block is 8x8 in y, potentially smaller if subsampled in chroma
     for by in 0..8 {
         for bx in 0..8 {
-            let global_block_offset = sbo_global.block_offset(bx, by);
-            if global_block_offset.x+bx < bc_global.cols && global_block_offset.y+by < bc_global.rows {
+            let global_block_offset = sbo_global.block_offset(bx<<1, by<<1);
+            if global_block_offset.x < bc_global.cols && global_block_offset.y < bc_global.rows {
                 let skip = bc_global.at(&global_block_offset).skip;
                 if !skip {
                     let dir = cdef_dirs.dir[bx][by];

src/rdo.rs

@@ -525,8 +525,8 @@ pub fn rdo_cdef_decision(sbo: &SuperBlockOffset, fi: &FrameInvariants,
         let mut err:u64 = 0;
         for by in 0..8 {
             for bx in 0..8 {
-                let bo = sbo.block_offset(bx, by);
-                if bo.x+bx < bc.cols && bo.y+by < bc.rows {
+                let bo = sbo.block_offset(bx<<1, by<<1);
+                if bo.x < bc.cols && bo.y < bc.rows {
                     let skip = bc.at(&bo).skip;
                     if !skip {
                         for p in 0..3 {