dlm: drop SCTP Kconfig dependency

DLM does not use any exported SCTP function. SCTP is registered
dynamically as protocol to the kernel and can be used over the right
protocol identifiers on the socket api. We drop the SCTP dependency as
DLM can also be used with TCP only.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Reviewed-by: Heming zhao <heming.zhao@suse.com>
Signed-off-by: David Teigland <teigland@redhat.com>