[fsp] Publish documentation for writable operations.

[fsp] Publish documentation for writable operations.

Writable operations are completed and pretty stable, so it's time to let
developers know about them and start using them!

TEST=Confirmed on a testing doc server.
BUG=248427
Committed: https://crrev.com/d548fc9e1f113a2d58623a160e08fc21d415a84c
Cr-Commit-Position: refs/heads/master@{#295838}

[mtomasz, 2014-09-19 02:31:00]

mtomasz@chromium.org changed reviewers:
+ miket@chromium.org

[mtomasz, 2014-09-19 02:31:08]

miket: PTAL. Thanks.

[miket_OOO, 2014-09-19 19:03:51]

lgtm

[mtomasz, 2014-09-20 00:35:19]

The CQ bit was checked by mtomasz@chromium.org

[commit-bot: I haz the power, 2014-09-20 00:37:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/583893002/1

[commit-bot: I haz the power, 2014-09-20 01:06:14]

Committed patchset #1 (id:1) as d1fd601edbd680d3d9fa2fa82c98ca5ccdf401c4

[commit-bot: I haz the power, 2014-09-20 01:06:55]

Patchset 1 (id:??) landed as
https://crrev.com/d548fc9e1f113a2d58623a160e08fc21d415a84c
Cr-Commit-Position: refs/heads/master@{#295838}