sctp: rename sctp_diag.c as diag.c

Remove 'sctp_' prefix for diag file, to keep consistent with other
files' names.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/Makefile

@@ -15,6 +15,8 @@ sctp-y := sm_statetable.o sm_statefuns.o sm_sideeffect.o \
 	  offload.o stream_sched.o stream_sched_prio.o \
 	  stream_sched_rr.o stream_interleave.o
 
+sctp_diag-y := diag.o
+
 sctp-$(CONFIG_SCTP_DBG_OBJCNT) += objcnt.o
 sctp-$(CONFIG_PROC_FS) += proc.o
 sctp-$(CONFIG_SYSCTL) += sysctl.o