Staging: batman-adv: check all kmalloc()s

there are some kmallocs left which are not checked whether they succeeds or
not, which might lead to corrupted data structures if the system memory is
full. This patch should clean up the remaining unchecked kmalloc()s.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>