ARM: dts: msm: Disable GPU mempool support for 8909w

Wearables are low-memory devices. Reserving
memory for GPU mempools on such targets often
leads to low-memory condition. So disable GPU
mempool on 8909 wearable.

Change-Id: I8e4103a77e1a211f7ad0b8a561033645b004c8a9
Signed-off-by: Sunil Khatri <sunilkh@codeaurora.org>