Revert "ARM: dts: msm: Update compatible string for saipan gpubw device"

This reverts commit cb8abf12.

The previous patch enabled the compatible string "devbw-ddr", which is
really needed if the SOC supports multiple DDR types. This is not
applicable for this platform. So this just reverts the previous patch.

Change-Id: I45a125b87e8197a2d828be37eb0004be2f160816