msm: kgsl: Use kernel defines to access 32bit values

Rather than writing our own functions to grab the upper and
lower 32 bits of a 64 bit number, use what the kernel
already has for us.

Change-Id: I7a583ba9cc793208bcf96af093870e7e567a5130
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>