dt-bindings: power: supply: charger-manager: Add missing type for 'cm-battery-stat'

'cm-battery-stat' is missing a type definition and is not a common
property. The type is boolean.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220719215017.1875530-1-robh@kernel.org