batman-adv: Move CRC16 dependency to BATMAN_ADV_BLA

The commit ced72933 ("batman-adv: use CRC32C instead of CRC16 in TT
code") switched the translation table code from crc16 to crc32c. The
(optional) bridge loop avoidance code is the only user of this function.

batman-adv should only select CRC16 when it is actually using it.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>