interface: backoff exponents print human readable
interface: backoff exponents print human readable

First print the minumum then the maxmimum backoff exponent attributes.

Signed-off-by: Alexander Aring <d03dbcdedb9639e397df9b8578e8fc8274f4e6c4@gmail.com>

cfriedt/wpan-tools,cfriedt/wpan-tools