Staging: batman-adv: Don't allocate icmp packet with GFP_KERNEL

A new buffer for a packet is created when a icmp packet is received.
This happens in a context with disabled irq. Thus we are not allowed to
sleep or call function which might sleep. kmalloc must be called with
GFP_ATOMIC instead of GFP_KERNEL to ensure that it does not sleep.

Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>