Return the more descriptive error codes instead of `EXDEV` when
the parameters don't match the requirements of the clone function.
Updated the comments in `brt.c` accordingly.
The first three errors are just invalid parameters, which zfs can
not handle.
The fourth error indicates that the block which should be cloned
is created and cloned or modified in the same transaction
group (`txg`).
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <rob.norris@klarasystems.com>
Signed-off-by: Kay Pedersen <mail@mkwg.de>
Closes#15148
895cb689d3