sctp: Don't abort initialization when CONFIG_PROC_FS=n

This puts CONFIG_PROC_FS defines around the proc init/exit functions
and also avoids compiling proc.c if procfs is not supported.
Also make SCTP_DBG_OBJCNT depend on procfs.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>