msm: kgsl: Populate the compat virtual pt regions for the secure pt

When mapping an external dma buffer, if the FORCE_32BIT flag is
set we use the compat_va_start and end to look for our gpuaddr.
Hence, we need to populate those fields when initializing the
secure pagetable.

Change-Id: Icbbf90c05fa2b949fb1191c6a89edad28392fc2a
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>