dt-bindings: battery: add new battery parameters

Add:

 - trickle-charge-current-microamp:

Some chargers have 3 charging stages. First one when battery is almost
empty is often called as trickle-charge. Last state when battery has been
"woken up" is usually called as fast-charge. In addition to this some
chargers have a 'middle state' which ROHM BD99954 data-sheet describes as
pre-charge. Some batteries can benefit from this 3-phase charging
[citation needed].

Introduce trickle-charge-current-microamp so that batteries can give
charging current limit for all three states.

 - precharge-upper-limit-microvolt:

When battery voltage has reached certain limit we change from
trickle-charge to next charging state (pre-charge for BD99954). Allow
battery to specify this limit.

 - re-charge-voltage-microvolt:

Allow giving a battery specific voltage limit for chargers which can
automatically re-start charging when battery has discharghed down to
this limit.

- over-voltage-threshold-microvolt

Allow specifying voltage threshold after which the battery is assumed to
be faulty.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>