net: sctp: fix array overrun read on sctp_timer_tbl

Table sctp_timer_tbl is missing a TIMEOUT_RECONF string so
add this in. Also compare timeout with the size of the array
sctp_timer_tbl rather than SCTP_EVENT_TIMEOUT_MAX.  Also add
a build time check that SCTP_EVENT_TIMEOUT_MAX is correct
so we don't ever get this kind of mismatch between the table
and SCTP_EVENT_TIMEOUT_MAX in the future.

Kudos to Marcelo Ricardo Leitner for spotting the missing string
and suggesting the build time sanity check.

Fixes CoverityScan CID#1397639 ("Out-of-bounds read")

Fixes: 7b9438de

 ("sctp: add stream reconf timer")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>