Merge branch 'sctp-size-validations'

Marcelo Ricardo Leitner says:

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sctp: add some size validations

Ilja Van Sprundel reported that some size validations on inbound
SCTP packets were missing. After some code review, I noticed two
others that are all fixed here.

Thanks Ilja for reporting this.
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Signed-off-by: David S. Miller <davem@davemloft.net>