cnic: use kvzalloc to allocate memory for csk_tbl

Size of csk_tbl is about 58K, which means 3rd order page allocation.
kvzalloc provides a fallback if no high order memory is available.

Signed-off-by: Jan Dakinevich <jan.dakinevich@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>