sctp: use GFP_KERNEL in sctp_init()

modules init functions being called from process context, we better
use GFP_KERNEL allocations to increase our chances to get these
high-order pages we want for SCTP hash tables.

This mostly matters if SCTP module is loaded once memory got fragmented.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>