Merge branch 'sctp-unify-sctp_make_op_error_fixed-and-sctp_make_op_error_space'

Marcelo Ricardo Leitner says:

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sctp: unify sctp_make_op_error_fixed and sctp_make_op_error_space

These two variants are very close to each other and can be merged
to avoid code duplication. That's what this patchset does.

First, we allow sctp_init_cause to return errors, which then allow us to
add sctp_make_op_error_limited that handles both situations.
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Signed-off-by: David S. Miller <davem@davemloft.net>