add a few informative printfs to if_bridge.c?

Hello all,

I've had some problems adding one if_ral interface to if_bridge device.
I've tracked down the problem to the MTU on my PCI if_ral interface
which is set to 2290 ( i think that hostapd did this ).

So, i have a proposition to add some informative printfs to if_bridge code,
because returning "Invalid argument" is not so self explanatory, especially
in the wrong MTU case. I think that most of the returns in bridge_ioctl_add(),
could benefit from additional printf with more information.
What do you think?


--niki