[ATM]: Remove unneeded kmalloc() return value casts + tiny whitespace cleanup

Small cleanups for drivers/atm/zatm.c
 Get rid of unneeded cast of kmalloc() return value.
 Small whitespace/CodingStyle/formatting cleanup (since I was in there anyway).

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>