msm: kgsl: Correct the inclusion of the sync_file.h

For QCOM_KGSL loadable module compilation sync_file.h
searched in the current source directory, which resulting
to compilation error. But header file is present in the
default linux include path. Correct the inclusion of header
file sync_file.h to search in a standard list of include path.

Change-Id: Ib90975dc281406a5b28ce436fd3b5094401f6300
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>