dt-bindings: power: supply: pm8941-charger: add pm8226

The charger in PM8226 (used in MSM8226) is similar to the charger in
PM8941.

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>