caif: Bugfix - handle mem-allocation failures

Discovered bugs when injecting slab allocation failures.
Add checks on all memory allocation.

Signed-off-by: Sjur Braendeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc net/caif/cfpkt_skbuff.c
Simple merge

diff --cc net/caif/cfserl.c
Simple merge

diff --cc net/caif/cfsrvl.c
Simple merge