The i.MX53 SoC has a PWM module, and Digi’s ConnectCore for MX53 module has a Dialog’s DA9052 PMIC with a PWM WLED module. These have different characteristics which are described on their respective datasheets.
The Freescale BSP does include a PWM module for the i.MX53 onchip PWM  which we don’t support in DEL/DEY and we have not integrated. If required, this integration work can be done through Etherios design services.
On DEL and DEY only the PMIC’s PWM controller is supported . This WLED module is ideal for driving display backlights, and that is what it is being used for in Dig’s BSP. It is also what it seems the customer needs.
As you say, there is no PWM support in u-boot, although we provide a “pmic” command which allows to access the PMIC’s registers, including those controlling the WLED PWM. This command could be used to script u-boot so that it configures the WLED at startup.