minorbug(dd): it do not show how many bytes copied

Hi, uutils mainteners

we confirmed a minor issue with the dd command i used

relunsec@relunsec:~/software/coreutils/target/debug$ sudo ./dd if=/dev/mem of=a
dd: IO error: Permission denied
relunsec@relunsec:~/software/coreutils/target/debug$ 

as you can see the content copied to a whiches good, but it stops after a permission denied, but it do not show how many bytes copied
while the gnu one does

relunsec@relunsec:~/software/coreutils/target/debug$ sudo gnudd if=/dev/mem of=a
gnudd: error reading '/dev/mem': Operation not permitted
2048+0 records in
2048+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0461996 s, 22.7 MB/s
relunsec@relunsec:~/software/coreutils/target/debug$ 

after the kernel error reached because the kernel block reading other regions, it showed how many bytes copied successfully before the error appeared

Start with the Rust implementation of the dd command and reproduce the /dev/mem read failure shown in the issue. Compare the error path with GNU dd's byte-count output; done means reporting how many bytes were copied successfully before a later permission error.