msm: kgsl: Add support for low memory GPU memory pool configuration

This change adds support to read low memory pool configuration if
device memory is less than 2GB. This is needed to optimize memory
footprint for targets which has SKUs with less than or equal to
2GB memory.

Change-Id: Ide733c792f7571d3db862a49cdf9cc73a3e94d1e
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>