msm: kgsl: Update global memory base to 0XFC000000 for 64bit kernel

KGSL memstore GPU address should be 32bit value for user mode
graphics driver to successfully mmap device memstore.

Move global memory base to 0XFC000000 from 0X100000000 for 64bit
kernel to allow user mode graphics driver to successfully mmap
memstore.

Change-Id: Iadfbde5e2b13c1be943a272e424f6c5f05cc1b97
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>