fix warning when egl is not there
fix warning when egl is not there

[ 32%] Building CXX object utests/CMakeFiles/utests.dir/utest_helper.cpp.o
/home/q/beignet.git/utests/utest_helper.cpp: In function ‘int cl_ocl_init()’:
/home/q/beignet.git/utests/utest_helper.cpp:314:8: warning: variable ‘hasGLExt’ set but not used [-Wunused-but-set-variable]

Signed-off-by: Lu Guanqun <2dad72ae5fe48bf7bd43ddccece96ab3f4a6c25d@intel.com>
Reviewed-by: Zhigang Gong <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@linux.intel.com>

zhenyw/beignet,ignatenkobrain/beignet,wdv4758h/beignet,ignatenkobrain/beignet,freedesktop-unofficial-mirror/beignet,zhenyw/beignet,freedesktop-unofficial-mirror/beignet,freedesktop-unofficial-mirror/beignet,freedesktop-unofficial-mirror/beignet,zhenyw/beignet,zhenyw/beignet,wdv4758h/beignet,wdv4758h/beignet,ignatenkobrain/beignet,wdv4758h/beignet,ignatenkobrain/beignet,wdv4758h/beignet,zhenyw/beignet,ignatenkobrain/beignet