dyndbg: give %3u width in pr-format, cosmetic only

Specify the print-width so log entries line up nicely.

no functional changes.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20200831182210.850852-2-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>