msm: kgsl: Fix check for oversized HFI messages

The check for HFI message size is incorrect as it is done
after the higher bits of size are masked out while creating
the HFI header. Fix the check so that we do not let oversized
messages through.

Change-Id: Ic2350da328d21f085bd41656d36c74132c5007ac
Signed-off-by: Sushmita Susheelendra <ssusheel@codeaurora.org>
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>