mfd: 88pm860x: Use REG in leds resource

Since the resources of 88pm860x leds are changed from IORESOURCE_IO
to IORESOURCE_REG that is register offset, change the original
self-defined IORESOURCE_IO to register offset.

Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>