[PPP]: handle kmalloc failures and convert to using kzalloc

The PPP code contains two kmalloc()s followed by memset()s without
handling a possible memory allocation failure.  (Suggested by Joe
Perches).

And furthermore, conversions from kmalloc+memset to kzalloc.

[akpm@osdl.org: fix error-path leak]
[akpm@osdl.org: cleanups]
[paulus@samba.org: don't add useless printk and cardmap_destroy calls]

Signed-off-by: Panagiotis Issaris <takis@issaris.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: David S. Miller <davem@davemloft.net>