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Based on the new opaque programmer framework this patch adds support
for Intel Hardware Sequencing on ICH8 and its successors.

By default (or when setting the ich_spi_mode option to auto)
the module tries to use swseq and only activates hwseq if need be:
- if important opcodes are inaccessible due to lockdown
- if more than one flash chip is attached.
The other options (swseq, hwseq) select the respective mode (if possible).

A general description of Hardware Sequencing can be found in this blog entry:
http://blogs.coreboot.org/blog/2011/06/11/gsoc-2011-flashrom-part-1/



Besides adding hwseq this patch also introduces these unrelated changes:

- Fix enable_flash_ich_dc_spi to pass ERROR_FATAL from ich_init_spi.
  The whole error handling looks a bit odd to me, so this patch does
  change very little. Also, it does not touch the tunnelcreek method,
  which should be refactored anyway.

- Add null-pointer guards to find_opcode and find_preop
  to matches the other opcode methods better:
  curopcodes == NULL has some meaning and is actively used/checked in
  other functions.

TODO: adding real documentation when we have a directory for it

Corresponding to flashrom svn r1461.
Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>