dt-bindings: leds: issi,is31fl319x: Drop 'db' suffix duplicating dtschema

A common property unit suffix '-db' was added to dtschema, thus
in-kernel bindings should not reference the type.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: "Rob Herring (Arm)" <robh@kernel.org>
Link: https://lore.kernel.org/r/20250811-dt-bindings-db-v1-1-457301523bb5@linaro.org


Signed-off-by: Lee Jones <lee@kernel.org>