simplify procfs code for seq_file instances

We currently have hundreds of proc files that implement plain, read-only
seq_file based interfaces.  This series consolidates them using new
procfs helpers that take the seq_operations or simple show callback
directly.

A git tree is available at:

    git://git.infradead.org/users/hch/misc.git proc_create

Gitweb:

    http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/proc_create

Diffstat:  268 files changed, 1193 insertions(+), 6194 deletions(-)

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