Fix zdb_dump_block for little endian (#16310)

The endian macros were changed but zdb_dump_block wasn't updated
accordingly.

Signed-off-by: Chunwei Chen <david.chen@nutanix.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Reviewed-by: Allan Jude <allan@klarasystems.com>