ARM: dts: msm: Remove GPU mempool for OpenQ 624

GPU mempool is required for graphics intensive operations.
OpenQ 624 does not support graphics intensive use cases.
Remove GPU mempool to free up the kernel memory.

Change-Id: I3261d9f0fac2f2aae690600c925338e75b7cae31
Signed-off-by: Vijay Navnath Kamble <vkambl@codeaurora.org>