leds: lm3692x: Allow to set ovp and brigthness mode

Overvoltage protection and brightness mode are currently hardcoded as 29V and disabled in the driver. Make these configurable via DT.

This v4 moves the exponential brightness mode to the back of the series as per Pavel's request:

https://lore.kernel.org/linux-next/20200106103233.GA32426@amd/T/#m93270a9bf10b88e060f4e4cf5701c527476de985

The end result is identical and i've tested everything still works when dropping the last to patches and checked compiltion via

git rebase -i ... -exec 'make ... Image dtbs'

Patches are against linux-leds-next.

Changes from v3
- Move exponential mode patches to the back of the series
https://lore.kernel.org/linux-next/20200106103233.GA32426@amd/T/#m93270a9bf10b88e060f4e4cf5701c527476de985
- Add Rob's Reviewed-by:, thanks!

Changes from v2
- As per review comment from Pavel Machek
https://lore.kernel.org/linux-leds/20191226100615.GA4033@amd/T/#u
- Use default value in DT example
https://lore.kernel.org/linux-leds/20191226100842.GC4033@amd/T/#u
- Use uppercase LED in commit message
https://lore.kernel.org/linux-leds/20191226101336.GD4033@amd/T/#u
- Fix typo in commit message
- Use correct return value when checking if property is present
- Fold in

    https://lore.kernel.org/linux-leds/20191226101419.GE4033@amd/T/#t

- Add Acked-By's from Pavel Machek, thanks!

Changes from v1
- As per review comments by Dan Murphy
https://lore.kernel.org/linux-leds/[email protected]/
- Split commits per propoerty
- Add new properties to DT example too
- Drop dev_dbg() statements
- ovp: fix 21V value parsing
- ovp: Set correct default value if DT parsing fails
- As per review comments by Pavel Machek
https://lore.kernel.org/linux-leds/20191221191515.GF32732@amd/
- Fix defaults (which is 29V)
- Use uV as Unit for ovp property
- Change property name to 'ti,ovp-microvolt' to make it shorter
- Honor led-max-microamp to not exceed the maximum led current

Guido Günther (6):
leds: lm3692x: Make sure we don't exceed the maximum led current
leds: lm3692x: Move lm3692x_init and rename to lm3692x_leds_enable
leds: lm3692x: Split out lm3692x_leds_disable
leds: lm3692x: Disable chip on brightness 0
dt: bindings: lm3692x: Add ti,brightness-mapping-exponential property
leds: lm3692x: Allow to configure brigthness mode

 .../devicetree/bindings/leds/leds-lm3692x.txt |   3 +
 drivers/leds/leds-lm3692x.c                   | 165 ++++++++++++------
 2 files changed, 113 insertions(+), 55 deletions(-)

2.23.0