batman-adv: directly write tt entries without buffering

When the translation tables (global and local) are written for debugfs,
it is not neccesary to allocate a buffer, we can directly use
seq_printf() to print them out.

This might actually be safer if the table changes between size
calculation and traversal, and we can't estimate the required size
wrong.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>