batman-adv: Remove extra check in batadv_bit_get_packet

batadv_bit_get_packet checks for all common situations before it decides that
the new received packet indicates that the host was restarted. This extra
condition check at the end of the function is not necessary because this
condition is always true.

This patch addresses Coverity #712296: Logically dead code

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>