net: sctp: fix incorrect type in gfp initializer

This fixes the following sparse warning:

  net/sctp/associola.c:1556:29: warning: incorrect type in initializer (different base types)
  net/sctp/associola.c:1556:29:    expected bool [unsigned] [usertype] preload
  net/sctp/associola.c:1556:29:    got restricted gfp_t

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>