ARM: dts: msm: Remove GPU mempool for msm8909

For low memory devices reserving memory can lead
to low-memory conditions. So remove GPU mempool
to have memory with the system, which will help
overall system performance in concurrent use cases.

CRs-Fixed: 2146074
Change-Id: I613e1d817b135940729d552a4d8d5a89d72c291c
Signed-off-by: Archana Obannagari <aobann@codeaurora.org>