watchdog: report all watchdog_ident information via sysfs

This synchronizes the information reported by ioctl and sysfs.
The mismatch is confusing because "wdctl" from util-linux uses the ioctl
when used with root privileges and sysfs without.

Userspace implementation: util-linux/util-linux#1927

To: Wim Van Sebroeck <wim@linux-watchdog.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-kernel@vger.kernel.org
Cc: linux-watchdog@vger.kernel.org
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
Changes in v3:
- EDITME: describe what is new in this series revision.
- EDITME: use bulletpoints and terse descriptions.
- Link to v2: https://lore.kernel.org/r/20221216-watchdog-sysfs-v2-0-6189311103a9@weissschuh.net


Changes in v2:
- Report options in addition to firmware_version
- Add documentation
- Rename firmware_version to fw_version to avoid conflicts
- Link to v1: https://lore.kernel.org/r/20221214-nsfs-ioctl-compat-v1-0-b169796000b2@weissschuh.net

--- b4-submit-tracking ---
# This section is used internally by b4 prep for tracking purposes.
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    "revision": 3,
    "change-id": "20221216-watchdog-sysfs-b2ce9f8f449b",
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      "v2": [
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