msm: kgsl: Use correct Highest Bank Bit (HBB) value for LPDDR3 on A702

LPDDR3 provides multiple config options based on DDR density. The HBB
values are different for various config options. As A702 supports LPDDR3,
query for the appropriate HBB value from device tree for LPDDR3 parts.

Change-Id: I60b469363636985963ada007f43196aa25608267
Signed-off-by: Puranam V G Tejaswi <pvgtejas@codeaurora.org>