caif: Remove OOM messages, use kzalloc

Remove per site OOM messages because they duplicate
the generic mm subsystem OOM message.

Use kzalloc instead of kmalloc/memset
when next to the OOM message removals.

Reduces object size (allyesconfig ~2%)

$ size -t drivers/net/caif/built-in.o.old net/caif/built-in.o.old
   text	   data	    bss	    dec	    hex	filename
  32297	    700	   8224	  41221	   a105	drivers/net/caif/built-in.o.old
  72159	   1317	  20552	  94028	  16f4c	net/caif/built-in.o.old
 104456	   2017	  28776	 135249	  21051	(TOTALS)
$ size -t drivers/net/caif/built-in.o.new net/caif/built-in.o.new
   text	   data	    bss	    dec	    hex	filename
  31975	    700	   8184	  40859	   9f9b	drivers/net/caif/built-in.o.new
  70748	   1317	  20152	  92217	  16839	net/caif/built-in.o.new
 102723	   2017	  28336	 133076	  207d4	(TOTALS)

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>