Merge branch 'sctp-Introduce-sctp_flush_ctx'

Marcelo Ricardo Leitner says:

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sctp: Introduce sctp_flush_ctx

This struct will hold all the context used during the outq flush, so we
don't have to pass lots of pointers all around.

Checked on x86_64, the compiler inlines all these functions and there is no
derreference added because of the struct.

This patchset depends on 'sctp: refactor sctp_outq_flush'

Changes since v1:
- updated to build on top of v2 of 'sctp: refactor sctp_outq_flush'

Changes since v2:
- fixed a rebase issue which reverted a change in patch 2.
- rebased on v3 of 'sctp: refactor sctp_outq_flush'
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Signed-off-by: David S. Miller <davem@davemloft.net>